Processes for preparing lithium hydroxide

ABSTRACT

There are provided system for preparing lithium hydroxide from an aqueous composition comprising a lithium compound and use of the system thereof to prepare lithium hydroxide, the system comprising an electrochemical cell, a pH probe and at least one inlet for receiving acid or base for maintaining pH. For example, the lithium compound can be lithium sulphate and the aqueous composition can be at least substantially maintained at a pH having a value of about 2 to about 4.

The present application is a continuation of U.S. Ser. No. 16/579,173filed on Sep. 23, 2019 that is a continuation of U.S. Ser. No.14/776,922 filed on Sep. 15, 2015 that is a 35 USC 371 national stateentry of PCT/CA2014/000264 filed on Mar. 17, 2014 and which claimspriority on U.S. Ser. No. 61/788,292 filed on Mar. 15, 2013. Thesedocuments are hereby incorporated by reference in their entirety.

The present disclosure relates to improvements in the field of chemistryapplied to the manufacture of lithium hydroxide. For example, suchprocesses are useful for preparing lithium hydroxide fromlithium-containing materials. For example, the disclosure also relatesto the production of other lithium products such as lithium carbonateand lithium sulphate.

The demand for lithium hydroxide is growing rapidly. The market forlithium hydroxide is expanding and the current world production capacitywill likely not meet the expected increase in demand. For example,lithium hydroxide is used for purification of gases and air (as a carbondioxide absorbent), as a heat transfer medium, as a storage-batteryelectrolyte, as a catalyst for polymerization, in ceramics, in Portlandcement formulations, in manufacturing other lithium compounds and inesterification, especially for lithium stearate.

Lithium batteries have become the battery of choice in several existingand proposed new applications due to their high energy density to weightratio, as well as their relatively long useful life when compared toother types of batteries. Lithium batteries are used for severalapplications such as laptop computers, cell phones, medical devices andimplants (for example cardiac pacemakers). Lithium batteries are also aninteresting option in the development of new automobiles, e.g., hybridand electric vehicles, which are both environmentally friendly and“green” because of reduced emissions and decreased reliance onhydrocarbon fuels.

High purity can be required for lithium hydroxide that is used, forexample, for various battery applications. There is a limited number oflithium hydroxide producers. As a direct result of increased demand forlithium products, battery manufacturers are looking for additional andreliable sources of high quality lithium products, for example lithiumhydroxide.

Few methods have been proposed so far for preparing lithium hydroxide.One of them being a method that uses natural brines as a startingmaterial. Battery applications can require very low levels ofimpurities, notably sodium, calcium and chlorides. The production oflithium hydroxide product with a low impurities content can be difficultunless one or more purification steps are performed. These additionalpurification steps add to the time and cost of the manufacture of thedesired lithium hydroxide product. Natural brines are also associatedwith high concentrations of magnesium or other metals which can makelithium recovery uneconomical. Thus, the production of lithium hydroxidemonohydrate from natural brines can be a difficult task.

There is thus a need for providing an alternative to the existingsolutions for preparing lithium hydroxide.

According to one aspect, there is provided a process for preparinglithium hydroxide, the process comprising:

submitting an aqueous composition comprising a lithium compound to anelectrolysis or an electrodialysis under conditions suitable forconverting at least a portion of the lithium compound into lithiumhydroxide.

According to another aspect, there is provided a process for preparinglithium hydroxide, the process comprising:

submitting an aqueous composition comprising a lithium compound to anelectrolysis or an electrodialysis under conditions suitable forconverting at least a portion of the lithium compound into lithiumhydroxide, wherein during the electrolysis or the electrodialysis, theaqueous composition comprising the lithium compound is at leastsubstantially maintained at a pH having a value of about 1 to about 4.

According to another aspect, there is provided a process for preparinglithium hydroxide, the process comprising:

submitting an aqueous composition comprising lithium sulphate to anelectrolysis or an electrodialysis under conditions suitable forconverting at least a portion of the lithium sulphate into lithiumhydroxide, wherein during the electrolysis or the electrodialysis, theaqueous composition comprising lithium sulphate is at leastsubstantially maintained at a pH having a value of about 1 to about 4.

According to another aspect, there is provided a process for preparinglithium hydroxide, the process comprising:

leaching an acid roasted lithium-containing material with water so as toobtain an aqueous composition comprising Li⁺ and at least one metal ion;

reacting the aqueous composition comprising Li⁺ and the at least onemetal ion with a base so as to obtain a pH of about 4.5 to about 6.5 andthereby at least partially precipitating the at least one metal ionunder the form of at least one hydroxide so as to obtain a precipitatecomprising the at least one hydroxide and an aqueous compositioncomprising Li⁺ and having a reduced content of the at least one metalion, and separating the aqueous composition from the precipitate;

contacting the aqueous composition comprising Li⁺ and having a reducedcontent of the at least one metal ion with an ion exchange resin so asto at least partially remove at least one metal ion from thecomposition, thereby obtaining an aqueous composition comprising alithium compound; and

submitting the aqueous composition comprising the lithium compound to anelectrolysis or an electrodialysis under conditions suitable forconverting at least a portion of the lithium compound into lithiumhydroxide.

According to another aspect, there is provided a process for preparinglithium hydroxide, the process comprising:

leaching a base-baked lithium-containing material with water so as toobtain an aqueous composition comprising Li⁺ and at least one metal ion;

reacting the aqueous composition comprising Li⁺ and the at least onemetal ion with a base so as to obtain a pH of about 4.5 to about 6.5 andthereby at least partially precipitating the at least one metal ionunder the form of at least one hydroxide so as to obtain a precipitatecomprising the at least one hydroxide and an aqueous compositioncomprising Li⁺ and having a reduced content of the at least one metalion, and separating the aqueous composition from the precipitate;

optionally reacting the aqueous composition comprising Li⁺ and havingthe reduced content of the at least one metal ion with another base soas to obtain a pH of about 9.5 to about 11.5, and with optionally atleast one metal carbonate, thereby at least partially precipitating atleast one metal ion optionally under the form of at least one carbonateso as to obtain a precipitate optionally comprising the at least onecarbonate and an aqueous composition comprising Li⁺ and having a reducedcontent of the at least one metal ion, and separating the aqueouscomposition from the precipitate;

contacting the aqueous composition comprising Li⁺ and having a reducedcontent of the at least one metal ion with an ion exchange resin so asto at least partially remove at least one metal ion from thecomposition, thereby obtaining an aqueous composition comprising alithium compound; and

submitting the aqueous composition comprising the lithium compound to anelectrolysis or an electrodialysis under conditions suitable forconverting at least a portion of the lithium compound into lithiumhydroxide.

According to another aspect, there is provided a process for preparinglithium hydroxide, the process comprising:

leaching a base-baked lithium-containing material with water so as toobtain an aqueous composition comprising Li⁺ and at least one metal ion;

optionally reacting the aqueous composition comprising Li⁺ and the atleast one metal ion with a base so as to obtain a pH of about 4.5 toabout 6.5;

at least partially precipitating the at least one metal ion under theform of at least one hydroxide so as to obtain a precipitate comprisingthe at least one hydroxide and an aqueous composition comprising Li⁺ andhaving a reduced content of the at least one metal ion, and separatingthe aqueous composition from the precipitate;

optionally reacting the aqueous composition comprising Li⁺ and havingthe reduced content of the at least one metal ion with another base soas to obtain a pH of about 9.5 to about 11.5, and with optionally atleast one metal carbonate, thereby at least partially precipitating atleast one metal ion optionally under the form of at least one carbonateso as to obtain a precipitate optionally comprising the at least onecarbonate and an aqueous composition comprising Li⁺ and having a reducedcontent of the at least one metal ion, and separating the aqueouscomposition from the precipitate;

contacting the aqueous composition comprising Li⁺ and having a reducedcontent of the at least one metal ion with an ion exchange resin so asto at least partially remove at least one metal ion from thecomposition, thereby obtaining an aqueous composition comprising alithium compound; and

submitting the aqueous composition comprising the lithium compound to anelectrolysis or an electrodialysis under conditions suitable forconverting at least a portion of the lithium compound into lithiumhydroxide.

According to another aspect, there is provided a process for preparinglithium hydroxide, the process comprising:

leaching an acid roasted lithium-containing material with water so as toobtain an aqueous composition comprising Li⁺ and at least one metal ion;

reacting the aqueous composition comprising Li⁺ and the at least onemetal ion with a base so as to obtain a pH of about 4.5 to about 6.5 andthereby at least partially precipitating the at least one metal ionunder the form of at least one hydroxide so as to obtain a precipitatecomprising the at least one hydroxide and an aqueous compositioncomprising Li⁺ and having a reduced content of the at least one metalion, and separating the aqueous composition from the precipitate;

optionally reacting the aqueous composition comprising Li⁺ and havingthe reduced content of the at least one metal ion with another base soas to obtain a pH of about 9.5 to about 11.5, and with optionally atleast one metal carbonate, thereby at least partially precipitating atleast one metal ion optionally under the form of at least one carbonateso as to obtain a precipitate optionally comprising the at least onecarbonate and an aqueous composition comprising Li⁺ and having a reducedcontent of the at least one metal ion, and separating the aqueouscomposition from the precipitate;

contacting the aqueous composition comprising Li⁺ and having a reducedcontent of the at least one metal ion with an ion exchange resin so asto at least partially remove at least one metal ion from thecomposition, thereby obtaining an aqueous composition comprising alithium compound; and

submitting the aqueous composition comprising the lithium compound to anelectrolysis or an electrodialysis under conditions suitable forconverting at least a portion of the lithium compound into lithiumhydroxide.

According to another aspect, there is provided a process for preparinglithium sulphate, the process comprising:

leaching an acid roasted lithium-containing material with water so as toobtain an aqueous composition comprising Li⁺ and at least one metal ion,wherein the lithium-containing material is a material that has beenpreviously reacted with H₂SO₄;

reacting the aqueous composition comprising Li⁺ and the at least onemetal ion with a base so as to obtain a pH of about 4.5 to about 6.5 andthereby at least partially precipitating the at least one metal ionunder the form of at least one hydroxide so as to obtain a precipitatecomprising the at least one hydroxide and an aqueous compositioncomprising Li⁺ and having a reduced content of the at least one metalion, and separating the aqueous composition from the precipitate; and

contacting the aqueous composition comprising Li⁺ and having a reducedcontent of the at least one metal ion with an ion-exchange resin so asto at least partially remove at least one metal ion from thecomposition, thereby obtaining an aqueous composition comprising alithium sulphate.

According to another aspect, there is provided a process for preparinglithium sulphate, the process comprising:

leaching an acid roasted lithium-containing material with water so as toobtain an aqueous composition comprising Li⁺ and at least one metal ion,wherein the lithium-containing material is a material that has beenpreviously reacted with H₂SO₄;

reacting the aqueous composition comprising Li⁺ and the at least onemetal ion with a base so as to obtain a pH of about 4.5 to about 6.5 andthereby at least partially precipitating the at least one metal ionunder the form of at least one hydroxide so as to obtain a precipitatecomprising the at least one hydroxide and an aqueous compositioncomprising Li⁺ and having a reduced content of the at least one metalion, and separating the aqueous composition from the precipitate;

optionally reacting the aqueous composition comprising Li⁺ and havingthe reduced content of the at least one metal ion with another base soas to obtain a pH of about 9.5 to about 11.5 and with at least one metalcarbonate thereby at least partially precipitating at least one metalion under the form of at least one carbonate so as to obtain aprecipitate comprising the at least one carbonate and an aqueouscomposition comprising Li⁺ and having a reduced content of the at leastone metal ion, and separating the aqueous composition from theprecipitate; and

contacting the aqueous composition comprising Li⁺ and having a reducedcontent of the at least one metal ion with an ion-exchange resin so asto at least partially remove at least one metal ion from thecomposition, thereby obtaining an aqueous composition comprising alithium sulphate.

In the following drawings, which represent by way of example only,various embodiments of the disclosure:

FIG. 1 is a block diagram concerning an example of a process accordingto the present disclosure;

FIG. 2 is a flow sheet diagram concerning another example of a processaccording to the present disclosure;

FIG. 3 is a plot showing lithium tenor as a function of time in anotherexample of a process according to the present disclosure;

FIG. 4 is a plot showing iron tenor as a function of time in anotherexample of a process according to the present disclosure;

FIG. 5 is a plot showing aluminum tenor as a function of time in anotherexample of a process according to the present disclosure;

FIG. 6 is a diagram showing various metals tenor as a function of timein another example of a process according to the present disclosure;

FIG. 7 is a plot showing various metals tenor as a function of time inanother example of a process according to the present disclosure;

FIG. 8 is a plot showing calcium tenor as a function of molar excess ofsodium carbonate in another example of a process according to thepresent disclosure;

FIG. 9 is a plot showing magnesium tenor as a function of molar excessof sodium carbonate in another example of a process according to thepresent disclosure;

FIG. 10 is a schematic representation of another example of a processaccording to the present disclosure;

FIG. 11 is a plot showing calcium tenor as a function of bed volumes inion exchange process in another example of a process according to thepresent disclosure;

FIG. 12 is a plot showing magnesium tenor as a function of bed volumesin the ion exchange process in another example of a process according tothe present disclosure;

FIG. 13 is a plot showing calcium tenor as a function of bed volumes inanother example of a process according to the present disclosure;

FIG. 14 is a plot showing magnesium tenor as a function of bed volumesin another example of a process according to the present disclosure;

FIG. 15 is a plot showing lithium tenor as a function of bed volumes inanother example of a process according to the present disclosure;

FIG. 16 is a plot showing various metals tenor as a function of bedvolumes in another example of a process according to the presentdisclosure;

FIG. 17 is a schematic representation of an example of a monopolarmembrane electrolysis cell that can be used for carrying out anotherexample of a process according to the present disclosure;

FIG. 18 is a plot showing current efficiency and concentration of H₂SO₄generated in the anolyte, concentration of LiOH generated in thecatholyte compartment during monopolar membrane electrolysis at 40degree C. as a function of charge passed in another example of a processaccording to the present disclosure;

FIG. 19 is a plot showing current efficiency and concentration at 40degree C. as a function of charge passed in another example of a processaccording to the present disclosure;

FIG. 20 is a plot showing current efficiency and concentration as afunction of charge passed in another example of a process according tothe present disclosure;

FIG. 21 is a plot showing current density, pH and conductivity profilesas a function of charge passed in another example of a process accordingto the present disclosure;

FIG. 22 is a plot showing current density, pH and conductivity profilesas a function of charge passed in another example of a process accordingto the present disclosure;

FIG. 23 is a plot showing current efficiency and concentration as afunction of charge passed in another example of a process according tothe present disclosure;

FIG. 24 is a plot showing current efficiency and concentration as afunction of charge passed in another example of a process according tothe present disclosure;

FIG. 25 is a plot showing current density, pH and conductivity profilesas a function of charge passed in another example of a process accordingto the present disclosure;

FIG. 26 is a plot showing current density, pH and conductivity profilesas a function of charge passed in another example of a process accordingto the present disclosure;

FIG. 27 is a plot showing current efficiency and concentration as afunction of charge passed in another example of a process according tothe present disclosure;

FIG. 28 is a plot showing current density, pH and conductivity profilesas a function of charge passed in another example of a process accordingto the present disclosure;

FIG. 29 is a plot showing concentration as a function of charge passedin another example of a process according to the present disclosure;

FIG. 30 is a plot showing current density, pH and conductivity profilesas a function of charge passed in another example of a process accordingto the present disclosure;

FIG. 31 is a plot showing current efficiency and concentration as afunction of charge passed in another example of a process according tothe present disclosure;

FIG. 32 is a schematic representation of an example of a membraneelectrolysis cell that can be used for carrying out another example of aprocess according to the present disclosure;

FIG. 33 is a schematic representation of an example of a configurationof a three compartment Bipolar Membrane Electrodialysis (EDBM) stackthat can be used for carrying out another example of a process accordingto the present disclosure;

FIG. 34 is a plot showing current intensity (A) as a function of time(minutes) in another example of a process according to the presentdisclosure;

FIG. 35 is a plot showing base conductivity (mS/cm) as a function oftime (minutes) in another example of a process according to the presentdisclosure;

FIG. 36 is a plot showing acid conductivity (mS/cm) as a function oftime (minutes) in another example of a process according to the presentdisclosure;

FIG. 37 is a schematic showing the loss of efficiency when the acid andbase loops reach a high concentration in another example of a processaccording to the present disclosure; and

FIG. 38 is a plot showing acid and base current efficiency as a functionof the concentration in another example of a process according to thepresent disclosure.

Further features and advantages will become more readily apparent fromthe following description of various embodiments as illustrated by wayof examples.

The term “suitable” as used herein means that the selection of theparticular conditions would depend on the specific manipulation oroperation to be performed, but the selection would be well within theskill of a person trained in the art. All processes described herein areto be conducted under conditions sufficient to provide the desiredproduct. A person skilled in the art would understand that all reactionconditions, including, when applicable, for example, reaction time,reaction temperature, reaction pressure, reactant ratio, flow rate,reactant purity, current density, voltage, retention time, pH, oxidationreduction potential, bed volumes, type of resin used, and recycle ratescan be varied to optimize the yield of the desired product and it iswithin their skill to do so.

In understanding the scope of the present disclosure, the term“comprising” and its derivatives, as used herein, are intended to beopen ended terms that specify the presence of the stated features,elements, components, groups, integers, and/or steps, but do not excludethe presence of other unstated features, elements, components, groups,integers and/or steps. The foregoing also applies to words havingsimilar meanings such as the terms, “including”, “having” and theirderivatives. The term “consisting” and its derivatives, as used herein,are intended to be closed terms that specify the presence of the statedfeatures, elements, components, groups, integers, and/or steps, butexclude the presence of other unstated features, elements, components,groups, integers and/or steps. The term “consisting essentially of”, asused herein, is intended to specify the presence of the stated features,elements, components, groups, integers, and/or steps as well as thosethat do not materially affect the basic and novel characteristic(s) offeatures, elements, components, groups, integers, and/or steps.

Terms of degree such as “about” and “approximately” as used herein meana reasonable amount of deviation of the modified term such that the endresult is not significantly changed. These terms of degree should beconstrued as including a deviation of at least ±5% or at least ±10% ofthe modified term if this deviation would not negate the meaning of theword it modifies.

The expression “at least one metal ion”, as used herein refers, forexample, to at least one type of ion of at least one metal. For example,the at least one metal ion can be M^(X+). In this example, M^(X+) is anion of the metal M, wherein X⁺ is a particular form or oxidation stateof the metal M. Thus, M^(X+) is at least one type of ion (oxidationstate X⁺) of at least one metal (M). For example, M^(Y+) can be anothertype of ion of the metal M, wherein X and Y are different integers.

The expression “is at least substantially maintained” as used hereinwhen referring to a value of a pH or a pH range that is maintainedduring a process of the disclosure or a portion thereof (for exampleheating, electrodialysis, electrolysis, etc.) refers to maintaining thevalue of the pH or the pH range at least 75, 80, 85, 90, 95, 96, 97, 98or 99% of the time during the process or the portion thereof.

The expression “is at least substantially maintained” as used hereinwhen referring to a value of a concentration or a concentration rangethat is maintained during a process of the disclosure or a portionthereof (for example heating, electrodialysis, electrolysis, etc.)refers to maintaining the value of the concentration or theconcentration range at least 75, 80, 85, 90, 95, 96, 97, 98 or 99% ofthe time during the process or the portion thereof.

The expression “is at least substantially maintained” as used hereinwhen referring to a value of a temperature or a temperature range thatis maintained during a process of the disclosure or a portion thereof(for example heating, electrodialysis, electrolysis, etc.) refers tomaintaining the value of the temperature or the temperature range atleast 75, 80, 85, 90, 95, 96, 97, 98 or 99% of the time during theprocess or the portion thereof.

The expression “is at least substantially maintained” as used hereinwhen referring to a value of an oxidation potential or an oxidationpotential range that is maintained during a process of the disclosure ora portion thereof (for example heating, electrodialysis, electrolysis,etc.) refers to maintaining the value of the oxidation potential or theoxidation potential range at least 75, 80, 85, 90, 95, 96, 97, 98 or 99%of the time during the process or the portion thereof.

The expression “is at least substantially maintained” as used hereinwhen referring to a value of an electrical current or an electricalcurrent range that is maintained during a process of the disclosure or aportion thereof (for example electrodialysis, electrolysis, etc.) refersto maintaining the value of the electrical current or the electricalcurrent range at least 75, 80, 85, 90, 95, 96, 97, 98 or 99% of the timeduring the process or the portion thereof.

The expression “is at least substantially maintained” as used hereinwhen referring to a value of a voltage or a voltage range that ismaintained during a process of the disclosure or a portion thereof (forexample electrodialysis, electrolysis, etc.) refers to maintaining thevalue of the voltage or the voltage range at least 75, 80, 85, 90, 95,96, 97, 98 or 99% of the time during the process or the portion thereof.

The below presented examples are non-limitative and are used to betterexemplify the processes of the present disclosure.

The processes of the present disclosure can be effective for treatingvarious lithium-containing materials. The lithium-containing materialcan be a lithium-containing ore, a lithium compound, or a recycledindustrial lithium-containing entity. For example, thelithium-containing ore can be, for example, α-spodumene, β-spodumene,lepidolite, pegmatite, petalite, eucryptite, amblygonite, hectorite,jadarite, smectite, a clay, or mixtures thereof. The lithium compoundcan be, for example, LiCl, Li₂SO₄, LiHCO₃, Li₂CO₃, LiNO₃, LiC₂H₃O₂(lithium acetate), LiF, lithium stearate or lithium citrate. Thelithium-containing material can also be a recycled industriallithium-containing entity such as lithium batteries, other lithiumproducts or derivatives thereof.

A person skilled in the art would appreciate that various reactionparameters such as, for example, reaction time, reaction temperature,reaction pressure, reactant ratio, flow rate, reactant purity, currentdensity, voltage, retention time, pH, oxidation reduction potential, bedvolumes, type of resin used, and/or recycle rates, will vary dependingon a number of factors, such as the nature of the starting materials,their level of purity, the scale of the reaction as well as all theparameters previously mentioned since they can be dependent from oneanother, and could adjust the reaction conditions accordingly tooptimize yields.

For example, during the electrodialysis or the electrolysis, the pH canbe at least substantially maintained at a value of about 1 to about 4,about 1 to about 2, about 1 to about 3, about 2 to about 3, or about 2to about 4. For example, during the electrolysis, the pH can be at leastsubstantially maintained at a value of about 1 to about 4, about 2 toabout 4 or about 2. For example, during the electrodialysis, the pH canbe at least substantially maintained at a value of about 1 to about 4 orabout 1 to about 2.

For example, the electrodialysis or the electrolysis can be carried outin a three-compartment membrane electrolysis or electrodialysis cell.

For example, the electrodialysis or the electrolysis can be carried outin a two-compartment membrane electrolysis or electrodialysis cell.

For example, the electrolysis can be carried out in a monopolarelectrolysis cell.

For example, the electrolysis can be carried out in a bipolarelectrolysis cell.

For example, the electrodialysis can be carried out in a bipolarelectrodialysis cell.

For example, the aqueous composition comprising lithium sulphate can besubmitted to an electrolysis. For example, the aqueous compositioncomprising the lithium compound can be submitted to a monopolar membraneelectrolysis process.

For example, the aqueous composition comprising the lithium compound canbe submitted to a monopolar three compartment membrane electrolysisprocess.

For example, the aqueous composition comprising lithium sulphate can besubmitted to an electrodialysis. For example, the aqueous compositioncomprising lithium sulphate can be submitted to a bipolar membraneelectrodialysis process. For example, the aqueous composition comprisingthe lithium compound can be submitted to a bipolar three compartmentmembrane electrodialysis process.

For example, the electrodialysis or the electrolysis can be carried outin an electrolytic cell in which a cathodic compartment is separatedfrom the central or anodic compartment by a cathodic membrane.

For example, the electrodialysis or the electrolysis can be carried outby introducing the aqueous composition comprising the lithium compound(for example LiCl, LiF, Li₂SO₄, LiHCO₃, Li₂CO₃, LiNO₃, LiC₂H₃O₂ (lithiumacetate), lithium stearate or lithium citrate) into a centralcompartment, an aqueous composition comprising lithium hydroxide into acathodic compartment, and an aqueous composition comprising an acid (forexample HCl, H₂SO₄, HNO₃ or acetic acid) into an anodic compartment. Theperson skilled in the art would understand that, for example, when LiClis introduced in the central compartment, HCl is generated in the anodiccompartment for example of a bipolar membrane electrodialysis cell. Forexample, when LiF is introduced in the central compartment, HF isgenerated in the anodic compartment for example of a bipolar membraneelectrodialysis cell. For example, when Li₂SO₄ is introduced in thecentral compartment, H₂SO₄ is generated in the anodic compartment forexample of a bipolar membrane electrodialysis cell. For example, whenLiHCO₃ is introduced in the central compartment, H₂CO₃ is generated inthe anodic compartment for example of a bipolar membrane electrodialysiscell. For example, when LiNO₃ is introduced in the central compartment,HNO₃ is generated in the anodic compartment for example of a bipolarmembrane electrodialysis cell. For example, when LiC₂H₃O₂ is introducedin the central compartment, acetic acid is generated in the anodiccompartment for example of a bipolar membrane electrodialysis cell. Forexample, when lithium stearate is introduced in the central compartment,stearic acid is generated in the anodic compartment for example of abipolar membrane electrodialysis cell. For example, when lithium citrateis introduced in the central compartment, citric acid is generated inthe anodic compartment for example of a bipolar membrane electrodialysiscell.

For example, the electrodialysis or the electrolysis can be carried outby introducing the lithium sulphate into a central compartment, anaqueous composition comprising lithium hydroxide into a cathodiccompartment, and an aqueous composition comprising sulphuric acid intoan anodic compartment.

For example, an anolyte can be used during the process that can compriseammonia. For example, an anolyte that comprises ammonia can be usedduring the process, thereby generating an ammonium salt.

For example, the process can further comprise adding gaseous or liquidammonia, i.e. NH₃ or NH₄OH at an anode or adjacently thereof, whereinthe anode is used for the process.

For example, the process can further comprise adding ammonia at an anodeor adjacently thereof, thereby generating an ammonium salt, wherein theanode is used for the process.

For example, the process can further comprise adding ammonia in ananolyte used for the process.

For example, the process can further comprise adding ammonia in ananolyte used for the process, thereby generating an ammonium salt.

For example, the ammonium salt can be (NH₄)₂SO₄.

For example, the electrodialysis or the electrolysis can be carried outby introducing the aqueous composition comprising the lithium compound(for example LiCl, LiF, Li₂SO₄, LiHCO₃, Li₂CO₃, LiNO₃, LiC₂H₃O₂ (lithiumacetate), lithium stearate or lithium citrate) into a centralcompartment, an aqueous composition comprising lithium hydroxide into acathodic compartment, and an aqueous composition comprising NH₃ into ananodic compartment. For example, when an aqueous composition comprisingNH₃ is introduced into the anodic compartment, proton-blocking membranesmay not be required and membranes which are capable, for example ofrunning at a temperature of about 80° C. and which may, for example,have lower resistance can be used. For example, the aqueous compositioncomprising the lithium compound can further comprise Na⁺.

For example, during the electrodialysis or the electrolysis, the aqueouscomposition comprising lithium hydroxide can be at least substantiallymaintained at a concentration of lithium hydroxide of about 1.5 M toabout 4.5 M, about 2 M to about 4 M, about 2.5 M to about 3.5 M, about3.1 M to about 3.3 M, about 35 to about 70 g/L or about 45 to about 65g/L.

For example, during the electrodialysis or the electrolysis, the aqueouscomposition comprising sulphuric acid can be at least substantiallymaintained at a concentration of sulphuric acid of about 0.5 M to about1.4 M, about 0.6 M to about 1.3 M, about 0.65 to about 0.85 M, about 0.7M to about 1.2 M, about 0.8 M to about 1.1 M, about 8.5 M to about 1.05M or about 0.9 M to about 1.0 M, about 20 to about 50 g/L, about 20 toabout 40 g/L, about 35 to about 70 g/L or about 25 to about 35 g/L.

For example, during the electrodialysis or the electrolysis, the aqueouscomposition comprising lithium sulphate can be at least substantiallymaintained at a concentration of lithium sulphate of about 5 to about 30g/L, about 5 to about 25 g/L, about 10 to about 20 g/L, or about 13 toabout 17 g/L.

For example, during the electrodialysis or the electrolysis, temperatureof the aqueous composition comprising lithium sulphate can be of about20 to about 80° C., about 20 to about 60° C., about 30 to about 40° C.,about 35 to about 65° C., about 40 to about 60° C., about 35 to about45° C., about 55 to about 65° C., about 50 to about 60° C., or about 46to about 54° C.

For example, during the electrodialysis or the electrolysis, temperatureof the aqueous composition comprising lithium sulphate can be at leastsubstantially maintained at a value of about 20 to about 80° C., about20 to about 60° C., about 30 to about 40° C., about 35 to about 65° C.,about 40 to about 60° C., about 35 to about 45° C., about 55 to about65° C., about 50 to about 60° C., or about 46 to about 54° C. Forexample, when an Asahi AAV or a similar anion exchange membrane is usedduring the electrodialysis or the electrolysis, temperature of theaqueous composition comprising lithium sulphate can be at leastsubstantially maintained at a value of about 40° C. For example, when aFumatech FAB or a similar anion exchange membrane is used during theelectrodialysis or the electrolysis, temperature of the aqueouscomposition comprising lithium sulphate can be at least substantiallymaintained at a value of about 60° C.

For example, a Nafion 324 or a similar cation exchange resin or membranecan be used during the electrodialysis or the electrolysis. Othermembranes such Nafion 902, Fumatech FKB, or Neosepta CMB may be used forhydroxide concentration.

For example, when an aqueous composition comprising NH₃ is introducedinto the anodic compartment during the electrodialysis or theelectrolysis, temperature of the aqueous composition comprising lithiumsulphate can be at least substantially maintained at a value of about 20to about 80° C., about 75 to about 85° C., about 20 to about 60° C.,about 30 to about 40° C., about 35 to about 65° C., about 40 to about60° C., about 35 to about 45° C., about 55 to about 65° C., about 50 toabout 60° C. or about 46 to about 54° C.

For example, during the electrodialysis or the electrolysis, electricalcurrent can be at least substantially maintained at a density of about50 to about 150 A/m², about 60 to about 140 A/m², about 70 to about 130A/m², about 80 to about 120 A/m², or about 90 to about 110 A/m².

For example, during the electrodialysis or the electrolysis, electricalcurrent can be at least substantially maintained at a density of about400 to about 3000 A/m², about 400 to about 2000 A/m², about 400 to about1500 A/m², about 400 to about 1200 A/m², about 400 to about 1000 A/m²,about 400 to about 600 A/m², about 425 to about 575 A/m², about 450 toabout 550 A/m² or about 475 to about 525 A/m².

For example, during the electrolysis, electrical current can be at leastsubstantially maintained at a density of about 700 to about 1200 A/m2.

For example, during the electrolysis, cell voltage can be at leastsubstantially maintained at a value of about 2 to about 10 V, about 3.0V to about 8.5 V, about 6.5 V to about 8 V, about 5.5 V to about 6.5 Vor about 6 V.

For example, during the electrodialysis or the electrolysis, voltage canbe at least substantially maintained at a value of about 4.5 V to about8.5 V, about 6.5 V to about 8 V, about 5.5 V to about 6.5 V or about 6V.

For example, during the electrodialysis or the electrolysis, electricalcurrent can be at least substantially maintained at a constant value.

For example, during the electrodialysis or the electrolysis, voltage canbe at least substantially maintained at a constant value.

For example, during the electrodialysis or the electrolysis, the overallLiOH current efficiency can be about 50% to about 90%, about 60% toabout 90%, about 60% to about 70%, about 60% to about 80%, about 65% toabout 85%, about 65% to about 80%, about 65% to about 75%, about 70% toabout 85% or about 70% to about 80%.

For example, during the electrodialysis or the electrolysis, the overallH₂SO₄ current efficiency can be about 55% to about 90%, about 60% toabout 85%, about 65% to about 80% or about 70% to about 80%.

For example, the aqueous composition comprising Li⁺ and at least onemetal ion can be reacted with the base so as to obtain a pH of about 4.8to about 6.5, about 5.0 to about 6.2, about 5.2 to about 6.0, about 5.4to about 5.8 or about 5.6.

For example, the aqueous composition comprising Li⁺ and at least onemetal ion can be reacted with lime.

For example, the at least one metal ion comprised in the aqueouscomposition that is reacted with the base so as to obtain a pH of about4.5 to about 6.5 can be chosen from Fe²⁺, Fe³⁺ and Al³⁺.

For example, the at least one metal ion comprised in the aqueouscomposition that is reacted with the base so as to obtain a pH of about4.5 to about 6.5 can comprise Fe³⁺.

For example, the at least one metal ion comprised in the aqueouscomposition that is reacted with the base so as to obtain a pH of about4.5 to about 6.5 can comprise Al³⁺.

For example, the at least one metal ion comprised in the aqueouscomposition that is reacted with the base so as to obtain a pH of about4.5 to about 6.5 can comprise Fe³⁺ and Al³⁺.

For example, the at least one hydroxide comprised in the precipitate canbe chosen from Al(OH)₃ and Fe(OH)₃.

For example, the precipitate can comprise at least two hydroxides thatare Al(OH)₃ and Fe(OH)₃.

For example, the base used so as to obtain a pH of about 4.5 to about6.5 can be lime.

For example, lime can be provided as an aqueous composition having aconcentration of about 15% by weight to about 25% by weight.

For example, the processes can further comprise maintaining the aqueouscomposition comprising Li⁺ and the at least one metal ion that isreacted with a base so as to obtain a pH of about 4.5 to about 6.5 at anoxidative potential of at least about 350 mV.

For example, the aqueous composition can be at least substantiallymaintained at an oxidative potential of at least about 350 mV bysparging therein a gas comprising O₂. For example, the gas can be air.Alternatively, the gas can be O₂.

For example, the processes can comprise reacting the aqueous compositioncomprising Li⁺ and having the reduced content of the at least one metalion with the another base so as to obtain a pH of about 9.5 to about11.5, about 10 to about 11, about 10 to about 10.5, about 9.8 to about10.2 or about 10.

For example, the base used so as to obtain a pH of about 9.5 to about11.5 can be NaOH or KOH.

For example, the base used so as to obtain a pH of about 9.5 to about11.5 can be NaOH.

The base and metal carbonate can be a mixture of aqueous NaOH, NaHCO₃,LiOH and LiHCO₃.

For example, the at least one metal carbonate can be chosen from Na₂CO₃,NaHCO₃, and (NH₄)₂CO₃.

For example, the at least one metal carbonate can be Na₂CO₃.

For example, the aqueous composition comprising Li⁺ and having thereduced content of the at least one metal ion can be reacted with theanother base over a period of time sufficient for reducing the contentof the at least one metal ion in the aqueous composition below apredetermined value. For example, the at least one metal ion can bechosen from Mg²⁺, Ca²⁺ and Mn²⁺. For example, the reaction can becarried out over a period of time sufficient for reducing the content ofCa²⁺ below about 250 mg/L, about 200 mg/L, about 150 mg/L, or about 100mg/L. For example, the reaction can be carried out over a period of timesufficient for reducing the content of Mg²⁺ below about 100 mg/L, about50 mg/L, about 25 mg/L, about 20 mg/L, about 15 mg/L or about 10 mg/L.

For example, the ion exchange resin can be a cationic resin.

For example, the ion exchange resin can be a cationic resin that issubstantially selective for divalent and/or trivalent metal ions.

For example, contacting with the ion exchange resin can allow forreducing a content of Ca²⁺ of the composition below about 10 mg/L, about5 mg/L, about 1 mg/L or about 0.5 mg/L.

For example, contacting with the ion exchange resin can allow forreducing total bivalent ion content such as Ca²⁺, Mg²⁺ or Mn²⁺, of thecomposition below about 10 mg/L, about 5 mg/L, about 1 mg/L or about 0.5mg/L.

For example, the acid roasted lithium-containing material can be leachedwith water so as to obtain the aqueous composition comprising Li⁺ and atleast three metal ions chosen from the following metals iron, aluminum,manganese and magnesium.

For example, the acid roasted lithium-containing material can be leachedwith water so as to obtain the aqueous composition comprising Li⁺ and atleast three metal ions chosen from Al³⁺, Fe²⁺, Fe³⁺, Mg²⁺, Ca²⁺, Cr²⁺,Cr³⁺, Cr⁶⁺, Zn²⁺ and Mn²⁺.

For example, the acid roasted lithium-containing material can be leachedwith water so as to obtain the aqueous composition comprising Li⁺ and atleast four metal ions chosen from Al³⁺, Fe²⁺, Fe³⁺, Mg²⁺, Ca²⁺, Cr²⁺,Cr³⁺, Cr⁶⁺, Zn²⁺ and Mn²⁺.

For example, the acid roasted lithium-containing material can beβ-spodumene that has been previously reacted with H₂SO_(4.)

For example, the acid roasted lithium-containing material can be aα-spodumene, β-spodumene, lepidolite, pegmatite, petalite, amblygonite,hectorite, smectite, clays, or mixtures thereof, that has beenpreviously reacted with H₂SO₄.

For example, the acid roasted lithium-containing material can beobtained by using a process as described in CA 504,477, which is herebyincorporated by reference in its entirety.

For example, the base-baked lithium-containing material can beβ-spodumene that has been previously reacted with Na₂CO₃ and with CO₂,and eventually heated.

In the processes of the present disclosure, the pH can thus becontrolled by further adding some base, some acid or by diluting. TheORP can be controlled as previously indicated by sparging air.

For example, when reacting the aqueous composition comprising Li⁺ andthe at least one metal ion with a base so as to obtain a pH of about 4.5to about 6.5 and thereby at least partially precipitating the at leastone metal ion under the form of at least one hydroxide so as to obtain aprecipitate, the metal of the at least one metal ion can be Fe, Al, Cr,Zn or mixtures thereof.

For example, when reacting the aqueous composition comprising Li⁺ andhaving the reduced content of the at least one metal ion with anotherbase so as to obtain a pH of about 9.5 to about 11.5, and withoptionally at least one metal carbonate, thereby at least partiallyprecipitating at least one metal ion, the metal of the at least onemetal ion can be Mn, Mg, Ca or mixtures thereof.

For example, when contacting the aqueous composition comprising Li⁺ andhaving a reduced content of the at least one metal ion with anion-exchange resin so as to at least partially remove at least one metalion, the at least one metal ion can be Mg²⁺, Ca²⁺ or a mixture thereof.

EXAMPLE 1

As shown in FIG. 1, lithium hydroxide can be obtained, for example, byusing such a process and by using a pre-leached lithium-containingmaterial as a starting material. For example, various leached ores suchas acid roasted β-spodumene can be used. The process shown in FIG. 1 canalso be used for producing lithium carbonate. According to anotherembodiment, the starting material can be a lithium compound such aslithium sulphate, lithium chloride or lithium fluoride. In such a case,the process would be shorter and would be starting at the box entitled“membrane electrolysis”.

Acid Roasted β-Spodumene (AR β-spodumene)

Two different blends of the AR β-spodumene were tested. The samples werecomposed of different ratios of the flotation and dense media separation(DMS) concentrates. The samples were identified as 75/25 and 50/50. Theformer sample contained about 75% by weight of the flotation concentrateand about 25% by weight of the DMS concentrate. The latter samplecontained substantially equal portions by mass of the two concentrates.The assay data of the feed samples is summarized in Table 1. The twosamples had very similar analytical profiles. The 75/25 sample hadhigher levels of Fe, Mn, Mg, Ca and K than the 50/50 sample. Bothsamples had typical compositions for AR β-spodumene.

TABLE 1 Assay Data of the AR β-Spodumene Samples Li Si Al Fe Na S Sample% 75/25 Comp 2.24 25.0 10.5 1.04 0.39 6.09 50/50 Comp 2.29 24.4 10.40.96 0.36 6.06 Cr Zn Mn Mg Ca K Sample g/t 75/25 Comp 167 134 1962 11863431 3653 50/50 Comp 163 103 1755  905 2311 3376

Concentrate Leach (CL) and Primary Impurity Removal (PIR)

The objectives of the Concentrate Leach (CL) and the Primary ImpurityRemoval (PIR) were 1) to dissolve lithium sulphate contained in the ARβ-spodumene and 2) to remove the major impurities from the processsolution that co-leach with lithium from the feed solids.

A four tank cascade was used for the combined CL and PIR process circuit(see FIG. 2). The AR β-spodumene was added using a feed hopper that wasequipped with a vibratory feeder. Each of the reactors was equipped withthe following: an overhead mixer motor (0.5 hp) with a 4-blade pitchimpeller attached, pH and ORP (Oxidation Reduction Potential) probes.The PIR reactors also had air spargers located directly below theimpeller. The process slurry flowed by gravity from one reactor to thenext through overflow ports. The overflow port of the CL reactor was setsuch that the active volume of the tank was about 32 L. The PIR reactorseach had an active volume of about 14 L. The overflow from PIR Tank 3(the last reactor of the tank train) was pumped to the filtrationstation.

About 1,200 kg of the 75/25 and about 1,400 kg of the 50/50 ARβ-spodumene samples were leached in about 85 hours of operation. Thechange over from one feed to the other occurred at the 37^(th) hour ofoperation. Time zero of the operation was when pulp began to overflowfrom the CL reactor.

In the CL step, water and solids were combined in an agitated tank at a50:50 weight ratio and mixed for about 30 to about 45 minutes underambient conditions. Lithium was extracted along with undesirable ganguemetals such as, for example, iron, aluminum, silicon, manganese, andmagnesium. The obtained slurry (CL slurry) thus comprised a solidcomposition and an aqueous (liquid) composition containing solubilizedLi⁺ (lithium ions) as well as solubilized ions of the above-mentionedmetals. The CL slurry pH and ORP were monitored but not controlled.Alternatively, the pH can eventually be controlled by further addingsome base, some acid or by diluting. The ORP can also be controlled aspreviously indicated by sparging air. The CL slurry flowed by gravity tothe PIR Tank 1. The aqueous composition can alternatively be separatedfrom the solid composition before being introduced in the PIR Tank 1 (orbefore carrying out PIR. In such a case, the aqueous composition(instead of the whole CL slurry as it is the case for the presentexample) would be inserted into Tank 1.

After 9 hours of operation there was sufficient volume of the Wash 1fraction (the first displacement wash fraction generated when washingthe combined CL and PIR solids residue) to recycle back to the CL. Theinitial recycle rate of the Wash 1 was set to about 50% of the wateraddition requirement of the CL. After 37 hours of operation, this amountwas increased to make-up 60% of the water addition to the process. Thiswash stream contained on average about 12 g/L Li (about 95 g/L ofLi₂SO₄).

Primary Impurity Removal (PIR) was carried out, for example, tosubstantially remove Fe, Al and Si from the aqueous composition whilesubstantially not precipitating any lithium. In this process, the pH ofthe concentrate leach slurry (comprising the aqueous composition and thesolid composition) was elevated to about 5.6 by lime slurry addition tothe three PIR tanks. The lime was added as a slurry having aconcentration of about 20 wt %. The CL slurry was thus converted into aprecipitate and an aqueous composition. The impurities such as Fe, Aland Si were at least substantially precipitated as insoluble metalhydroxides and found in the precipitate while the lithium ions weresubstantially found in the aqueous composition. The retention time forthe PIR circuit was about 45 to about 60 minutes. Air was sparged intothe PIR tanks in order to maintain the oxidative potential of theprocess slurry at or above about 350 mV. At this level, iron present inthe ferrous (Fe²⁺) form would likely oxidize to ferric iron (Fe³⁺), aform suitable for precipitation at such a pH. Thus, a precipitatecomprising, for example, metal hydroxides of Fe, Al and Si was obtainedand eventually separated from the aqueous composition comprising lithiumions. In the PIR, the pH can thus be controlled by further adding somebase, some acid or by diluting. The ORP can be controlled as previouslyindicated by sparging air.

The resulting slurry (comprising the aqueous composition and the solidcomposition (comprising the precipitate)) was filtered on pan filters.The filtrate (aqueous composition comprising lithium ions and having areduced content of the above mentioned metals (such as Fe, Al and Si))proceeded to Secondary Impurity Removal (SIR). The PIR filter cakeunderwent three displacement washes with site water. The first washfraction was collected separately from the second two washes. The firstwash stream was recycled to the CL process as a portion of the waterfeed stream to recover the contained lithium. Wash fractions 2 and 3were combined and stored as a solution. This solution can be used forlime slurry make-up to recover the lithium units.

The lithium tenors in CL and PIR are presented in FIG. 3. At hour 9, thefirst wash fraction from PIR was recycled back to the CL tank to make-uphalf of the water addition to the leach. Lithium tenors increasedthroughout the circuit to about 18 g/L (about 142.6 g/L of Li₂SO₄) as aresult. At hour 37.5, the recycle rate was increased to make-up 60% ofthe water to the leach and lithium tenors increased to about 25 g/L(about 198 g/L of Li₂SO₄). The PIR first wash lithium tenors ranged fromabout 12 to about 15 g/L (about 95 g/L to about 118.8 g/L of Li₂SO₄).

The pH was substantially steady throughout the operation once thethroughput was reduced. The ORP of the slurry in PIR tank 3 wassubstantially steady and above about 350 mV during the operation. Theiron tenors for CL and PIR are presented in FIG. 4. At hours 10 and 54,the pH of PIR3 was near a value of about 5.6 and yet the iron tenor inthe PIR3 liquor increased.

Iron and aluminum profiles are presented in FIGS. 4 and 5. Both iron andaluminum showed increasing levels in the CL tank throughout the run.Iron levels maintained below about 5 mg/L in PIR3 for most of the runregardless of the increase observed in CL. Aluminum in PIR3 was lessthan about 10 mg/L for the first 40 hours, and then ranged between about20 and about 65 mg/L for the remainder of the operating time.

A mass balance for the CL and PIR circuits is shown in Table 3. Lithiumextraction and impurity precipitation is calculated based on solidsassays. The mass balance shows that overall about 82% of the lithiumpresent in the AR β-spodumene feed proceeded to Secondary ImpurityRemoval (SIR). Specifically, about 79% lithium extraction was achievedfor the 75/25 blend and about 86% for the 50/50 blend. The portions ofaluminum and iron that either did not leach or precipitated totaledabout 96% and about 99%, respectively.

TABLE 3 Mass Balance of CL and PIR circuits Metal Content, mg/L or %Quan- Li Dens- Process Streams tity, % or Al Fe Cr Zn Process Streamsity % Metal Units, g INPUTS Op Hr kg mg/L g/t or mg/L INPUTS Op Hr kg/LSolids Li Al Fe Cr Zn AR B-Spodumene AR B-Spodumene 13.5 485 2.25 1069099792 173 130 13.5 10912 51847 4749 84 63 25.5 436 2.19 102675 10072 192154 25.5 9555 44797 4394 84 67 37.5 323 2.15 101087 10352 211 177 37.56938 32621 3340 68 57 49.5 407 2.21 104792 11261 212 148 49.5 8995 426534583 86 60 61.5 435 2.28 106909 8883 212 119 61.5 9907 46455 3860 92 5273.5 363 2.31 107438 8813 182 88 73.5 8397 39053 3203 66 32 80.0 2052.31 107438 8813 182 88 80.0 4732 22007 1805 37 18 PIR Wash 1 PIR Wash 113.5 113 11200 77 11.2 <0.2 5.6 13.5 1.06 1195 8 1 0 1 25.5 252 11200 7711.2 <0.2 5.6 25.5 1.07 2631 18 3 0 1 37.5 214 11200 77 11.2 <0.2 5.637.5 1.06 2262 15 2 0 1 49.5 273 15300 65 4.3 <0.2 5.9 49.5 1.10 3800 161 0 1 61.5 273 15300 65 4.3 <0.2 5.9 61.5 1.12 3748 16 1 0 1 73.5 24912300 64 3.1 <0.2 3.5 73.5 1.09 2821 15 1 0 1 80.0 157 12600 62 1.5 <0.23.6 80.0 1.08 1829 9 0 0 1 OUTPUTS Li Al Fe Cr Zn OUTPUTS Li Al Fe Cr ZnPIR3 Solids PIR3 Solids 13.5 536 0.60 26491 11960 247 133 13.5 47.2 321867836 6414 132 71 25.5 277 0.40 21198 11471 229 160 25.5 30.1 1107 335343174 63 44 37.5 268 0.58 19611 13219 211 187 37.5 36.3 1556 32094 354757 50 49.5 333 0.31 23315 13079 211 164 49.5 39.3 1032 41042 4353 70 5461.5 294 0.46 26491 11051 210 140 61.5 33.6 1354 37238 3253 62 41 73.5282 0.48 24374 10771 201 141 73.5 36.8 1353 35070 3037 57 40 80.0 1690.50 25962 11051 201 141 80.0 36.8 844 21268 1866 34 24 PIR3 SolutionPIR3 Solution 13.5 600 10700 37.3 60.5 <0.2 5.5 13.5 1.07 5995 21 34 0 325.5 642 20100 6.95 1.05 <0.2 3.9 25.5 1.12 11477 4 1 0 2 37.5 470 164001.3 0.8 <0.2 1.7 37.5 1.11 6970 1 0 0 1 49.5 515 24550 36.45 3.3 <0.25.4 49.5 1.15 10953 16 1 0 2 61.5 582 23500 71 3.2 <0.2 4.6 61.5 1.1511926 36 2 0 2 73.5 484 22800 19.5 2.15 <0.2 3.45 73.5 1.15 9580 8 1 0 180.0 290 25900 65.5 3.4 <0.2 4.8 80.0 1.16 6464 16 1 0 1 Units IN 13.512107 51855 4750 84 64 25.5 12186 44815 4397 84 68 37.5 9200 32636 334368 58 49.5 12795 42669 4585 86 62 61.5 13655 46471 3861 92 53 73.5 1121839068 3204 66 33 80.0 6560 22017 1805 37 19 TOTAL 77722 279532 25945 517356 Units OUT 13.5 9212 67857 6448 132 74 25.5 12584 33538 3174 63 4637.5 8527 32095 3547 57 51 49.5 11985 41058 4355 70 57 61.5 13281 372743255 62 44 73.5 10934 35078 3038 57 41 80.0 7308 21284 1867 34 25 TOTAL73830 268184 25684 475 338 Extraction 13.5 71 25.5 88 37.5 78 49.5 8961.5 86 73.5 84 80.0 82 TOTAL 82 Precipitation 13.5 131 135 158 113 25.575 72 76 66 37.5 98 106 83 88 49.5 96 95 81 90 61.5 80 84 67 80 73.5 9095 86 124 80.0 97 103 91 132 TOTAL 96 99 92 93 Accountability, OUT/IN %76 131 136 158 117 103 75 72 76 68 93 98 106 83 87 94 96 95 81 92 97 8084 67 82 97 90 95 86 126 111 97 103 91 135 TOTAL 95 96 99 92 95*Averages if shown in italics

Secondary Impurity Removal

Secondary Impurity Removal (SIR) was performed on the PIR filtrate(aqueous composition comprising lithium ions and having a reducedcontent of the above mentioned metals (such as Fe, Al and Si)) tosubstantially precipitate and remove Ca, Mg and Mn impurities therefrom.Feed addition to the SIR circuit started at operating hour 6 (six hoursafter overflow from the CL tank). There are four process tanks arrangedin a cascade (see FIG. 2). The tank volumes could be adjusted during therun from about 11.8 to about 17.5 L by changing the tank overflow ports.All tanks are baffled and agitated by overhead mixers. pH, ORP andtemperature were monitored in all tanks.

In the first two agitated tanks, the pH was increased to about 10 usingabout 2 M sodium hydroxide (NaOH) (another base). Following this pHadjustment, an excess of sodium carbonate (Na₂CO₃) based on levels oftargeted impurities in the feed was added to the third tank to convertthe remaining divalent impurities to insoluble carbonates. The slurryfrom the third tank was pumped to a clarifier. Underflow solids wereremoved and recovered by filtration while the overflow solution wascollected in an about 1000 L tote.

Averaged impurity tenors of solutions from the Concentrate Leach stagethrough to the final tank of Secondary Impurity Removal are shown inTable 4 and FIG. 6.

TABLE 4 Profile of Selected Impurities Li Al Fe Cr Zn Mn Mg Ca Streammg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L CL 23880 1737 985 5.9 9.1 178109 468 PIR1 21290  34  9 0.0 4.3 174 153 435 PIR2 21240  28  8 0.0 4.0173 175 433 PIR3 21140  30  8 0.0 4.2 174 179 434 SIR1 20093   1  0 0.00.0  2  43 426 SIR2 22500   0  0 0.0 0.0  1  19 352 SIR3 19050   1  00.0 0.0  1  16 322 SIR4 22400   0  0 0.0 0.0  1  14 241

Impurities introduced in the leach stage included iron, aluminum,chromium, zinc, magnesium, manganese and calcium. Substantially all ofthe chromium and over about 98% of the iron and aluminum substantiallyprecipitated in the first PIR tank (PIR1). Minimal precipitationoccurred in the next two tanks of PIR (PIR2 and PIR3). By the first tankof SIR (SIR1), the only impurities substantially remaining in solutionwere magnesium and calcium. All other elements were less than about 1mg/L. Although most of the precipitation occurred in SIR1, the extraretention time of SIR2 dropped the magnesium tenor from about 40 toabout 20 mg/L. From SIR2 through SIR4, magnesium and calcium tenorsshowed a steady decline with more retention time. Impurity levels forSIR4 averaged to about 1 mg/L Mn, about 14 mg/L Mg and about 241 mg/L Caduring the pilot plant run. However, levels as low as about 200 mg/L Caand about 2 mg/L Mg were attained by the optimization of key parameters.

pH and ORP were monitored throughout the operation. pH was onlycontrolled in the first two tanks. Initially, the selected pH for SIR2was about 10. At operating hour 30, the pH in SIR2 was increased toabout 10.5. With the exception of a 2-hour period at hour 50, where thepH in SIR2 dropped to about 10, pH remained at about 10.5 for theremainder of the run. The average pH values achieved over the twoperiods were about 10.1 and about 10.5 and the resulting sodiumhydroxide consumptions were about 0.022 and about 0.024 kg sodiumhydroxide per hour, respectively. The overall sodium hydroxideconsumption was about 10 kilograms of sodium hydroxide solution perabout 1000 kg of lithium carbonate equivalent (LCE).

The impurity tenors of SIR2 solutions are plotted over time in FIG. 7.These solutions have been pH adjusted by sodium hydroxide to above 10,but have not yet been dosed with sodium carbonate. Magnesium tenors arelower after the adjustment, but the levels show a gradual trenddownwards that appears to begin prior to the set point change. It shouldbe noted that later in the pilot plant, the retention time was increasedfor all SIR tanks, which may have also contributed to improvedprecipitation performance.

Calcium and magnesium tenors in solutions leaving SIR4 are plotted inFIGS. 8 and 9. These Figures relate impurity tenor (Mg and Ca only) withthe sodium carbonate dosage used at the time the sample was taken.Additionally, the data are plotted based on the retention times of theentire SIR circuit at the time of each sample. Within the range tested,as the sodium carbonate increased, metal tenors decreased. It should benoted that the lowest impurity tenors also corresponded with greatercircuit retention time. Sodium carbonate dosage is expressed as molarexcess of calcium impurities present prior to sodium carbonate addition(using assays from SIR2). The data indicated that the solution tenor ofCa can decrease to below about 200 mg/L.

Product from the SIR circuit was assayed every about 4 hours as it leftthe final tank (SIR4) (see FIG. 2). The SIR4 product was pumped into anabout 100 L clarifier and the overflow from the clarifier was filteredthrough an about 0.5 pm spiral wound cartridge filter and then collectedin about 1000 L plastic totes. These totes were assayed again to confirmbulk calcium feed tenors for Ion Exchange (IX). When the totes weresampled light brown solids were observed in the bottom of each tote.Assays revealed a significant drop in calcium tenor from the solutionsleaving the final tank of the circuit (SIR4) to the solution sittingunmixed in the totes. A comparison of the average assays for bothstreams is presented in Table 5, below.

TABLE 5 Effect of Aging on SIR Product Mg Ca Stream mg/L mg/L SIR4Product 17 286 IX Feed Tote 15 140

A mass balance for the SIR circuit is shown in Table 6. The mass balanceshows that overall about 92% of the magnesium and all of the manganesereported to the solids. The distribution of lithium to the solids isabout 0.9% for an overall SIR lithium recovery of about 99.1%.

TABLE 6 Mass Balance of SIR circuit Metal Content, mg/L or % ProcessStreams Quantity, Mn Mg Ca Process Streams Density Metal Units, g INPUTSOp Hr kg g/t or mg/L INPUTS Op Hr kg/L Mn Mg Ca SIR Feed SIR Feed 13.5600 72 69 438 13.5 1.08 40 38 242 25.5 642 109 111 463 25.5 1.03 68 69288 37.5 470 146 209 459 37.5 1.12 62 88 193 49.5 515 199 216 451 49.51.14 90 97 203 61.5 582 227 181 415 61.5 1.10 121 96 220 73.5 484 203154 441 73.5 1.20 81 62 177 80.0 290 195 150 443 80.0 1.17 48 37 109OUTPUTS Mn Mg Ca OUTPUTS Mn Mg Ca SIR Solids SIR Solids  Solids Pail 13.17 64700 63600 86300  Solids Pail 1 205 201 273  Solids Pail 2 4.0368000 54700 85200  Solids Pail 2 274 221 343 SIR4 Solution SIR4 Solution13.5 176 0.7 18 309 13.5 1.05 0 3 52 25.5 383 1.2 21 358 25.5 1.09 0 7126 37.5 426 1.6 48 370 37.5 1.11 1 18 143 49.5 395 0.1 20 325 49.5 1.150 7 112 61.5 208 0.2 7.6 191 61.5 1.15 0 1 35 73.5 214 0.2 1.4 220 73.51.20 0 0 39 80.0 206 0.4 1.5 225 80.0 1.21 0 0 38 SIR Lithium RecoveryPrecipitation = (1 - SIR4 solution / SIR Feed)*100 SIR solids, kg Li 0.3 13.5 100 92 79 SIR total out, kg Li 36.3 25.5 99 89 56 LithiumRecovery, % 99.1 37.5 99 79 26 49.5 100 93 45 61.5 100 99 84 73.5 100100 78 80.0 100 99 65 TOTAL 100 92 62 Accountability, OUT/IN % 94 94 81Distribution to Solids 100 92 53

Ion Exchange

The SIR product is processed through an ion-exchange (IX) circuit tofurther reduce the Ca and Mg tenors prior to lithium product production.The IX circuit comprises three columns packed with Purolite™ S950, acationic resin that can be used in the sodium form that is selectivetowards divalent and trivalent metal ions. Purolite™ S950 comprises anaminophosphonic resin supported on a macroporous cross-linked polymer.It can be used for the removal of heavy metal cations. At high pH it canbe active in the removal of Group 2 metal cations (Mg, Ca and Ba) andCd, Ni and Co. At high pH divalent metal cations are preferentiallyabsorbed over monovalent metal cations (e.g. Li, Na, K). Any ionexchange resin that would be suitable for substantially selectivelyremoving divalent metal cations such as Ca²⁺ and Mg²⁺ and/or trivalentmetal cations could be alternatively used in the present disclosure.Alternatively, more than one type of resin can be used to selectivelyremove the various metal cations. Thus, different ion exchange resinscan be used for different metal cations.

The operating philosophy used for the IX circuit was a Lead-LagRegeneration process (see FIGS. 2 and 10). Two of the IX columns of thecircuit are involved with Ca and Mg removal, while the resinregeneration cycle is conducted on the third column. A schematicillustrating the solution flow through the IX circuit and the lead-lagregeneration operation is provided in FIG. 10. The loading of Ca and Mgwill take place on two columns denoted lead and lag and will produce aneffluent having both Ca and Mg solution tenors below about 10 mg/L. Theloaded column undergoes stripping and regeneration stages prior to beingreintroduced as the lag column for the next loading cycle. The columnswere constructed from clear PVC pipe. Each column had a diameter ofabout 15 cm and a height of about 76 cm. The bed volume of each columnwas about 10 L.

The parameters for the IX operation are summarized in Table 7. Theseparameters were based on the laboratory tests results and the Lead-Lagcolumn configuration was designed to process 75 bed volumes (BV) of feedsolution before the Ca and Mg tenors in the Lag effluent exceededestablished upper limit that was about 10 mg/L that was established foreach cation. After processing 75 BV's of feed solution the combinedabsorption capacity of the resin in the Lead and Lag columns would notbe sufficient to produce a final effluent with the Ca and Mg tenors eachbelow about 10 mg/L. At this point the loading cycle is complete. TheLead column is promoted to the Regeneration stage. The Lag column takesthe Lead position. The Regenerated column becomes the Lag column.

The Regeneration stage involved washing the Lead column with reverseosmosis (RO) water to flush out the Li rich solution within the column.This solution is passed to the Lag column. The Feed Wash stage isfollowed by Acid Strip using about 2 M HCl. This removes the absorbedCa, Mg, Li and other metal cations from the resin. The resin is now inthe acid form. An Acid Wash stage follows to rinse the remaining HCl(aq)from the column. The resin is then converted to the Na form by passingabout 2 M NaOH through the column (Regeneration Stage). The final stepinvolves washing the excess NaOH from the column using reverse osmosis(RO) water. The resin is now regenerated and ready to be promoted to theLag position for the next Loading cycle. The effluent from the AcidStrip cycle was collected separately. The effluents from the Acid Wash,Regeneration and Regeneration Wash cycles were all captured in the samedrum.

The Acid Strip stage produces a solution that contains Li, Ca, and Mg.The data indicated that Li elutes from the column first followed by Caand Mg. It can be possible to separately capture the Li fraction and asa result produce a lithium chloride solution.

TABLE 7 IX Pilot Operation Parameters Bed Volume Rate, IX Stage Solution(BV) BV/h Loading IX Feed 75 5 Feed Wash RO Water 1.5 5 Acid Strip 2MHCl 3 5 Acid Wash RO Water 5 5 Regeneration 2M NaOH 3 5 RegenerationWash RO Water 3 5 1 BV = 10 L

A total of about 2154 L of SIR Product solution was processed throughthe IX circuit in four cycles. The average Li, Ca, and Mg tenors of thefeed solutions for each cycle are summarized in Table 8.

TABLE 8 IX-Average Feed Solution Li, Ca and Mg Tenors Average FeedSolution Tenor, mg/L IX Cycle Li Ca Mg C1 16480 176 28.2 C2 17600 14012.9 C3 & C4 21940 78.7 3.6

A cycle was initially designed to operate the Loading stage for 75 BV's.The average loading flow rate was about 832 mL/min (about 49.9 L/h).Cycle 1 was the only cycle where 75 BVs of feed solution was passedthrough the Lead-Lag columns.

The Ca Loading curve for Cycle 1, where the Ca tenor of the effluentsfrom the Lead and Lag columns are plotted against cumulative bed volumeprocessed, is presented in FIG. 11. Also plotted on this plot is theaverage Ca tenor in the feed solution and the selected limit for Catenor in the Lag effluent (about 10 mg/L) for the present example. Thebreakthrough point for Ca of the Lead column occurred at 7.5 BV. The Catenor of the Lead effluent was about 82.3 mg/L after 75 BV's indicatingthat the loading capacity of the Lead column was not reached for Ca. Thebreakthrough point for Ca of the Lag column occurred at about 35 BV. TheCa tenor in the Lag effluent increased above about 10 mg/L between the60^(th) and 65^(th) BV. It was decided to continue the Loading stage ofCycle 1 through to the 75^(th) BV point even though the Lag effluent wasabove about 10 mg/L of Ca. The effluent from the 65^(th) to 75^(th) BVpoint was diverted to an about 200 L drum and kept separate from themain product solution of Cycle 1. The diverted solution was latercombined with the main Cycle 1 product when it was determined that theCa tenor in the resulting combined solution would not exceed about 10mg/L.

A similar loading profile for Mg for Cycle 1 is presented in FIG. 12.The average Mg tenor in the feed solution and for example an upper limitof Mg tenor in the Lag effluent (about 10 mg/L) are also included inthis plot. The breakthrough point for Mg of the Lead column occurred at7.5 BV's. After 75 BV's the Mg tenor of the Lead effluent was about 9.5mg/L. The breakthrough point for Mg of the Lag column occurred at 52.5BV's. After 75 BV's the Mg tenor of the Lag effluent was about 0.8 mg/L,well below the selected limit level for Mg in the IX product solution,according to this example.

Cycles 2 and 3 had to be stopped before 75 BV's of feed solution couldbe processed through the columns. The Ca tenors of the Lag effluent foreach IX cycle are plotted against cumulative BV in FIG. 13. In the caseof Cycle 2 the Ca breakthrough points for the Lead and Lag columnsoccurred at < about 7.5 and about 23 BV, respectively. Cycle 2 wasstopped after about 68 BV. The Ca in the Lag effluent had reached about13 mg/L at after about 60 BV's. Breakthrough of Ca for the Lag column ofCycle 3 occurred within the first 5 BV's. Cycle 3 was stopped afterabout 30 BV's. The tenor of the Ca in the Lag effluent at the 30 BVpoint was about 7.7 mg/L.

The balance of the Cycle 3 feed solution was processed over about 36.4BV's in Cycle 4. The Ca breakthrough points for the Lead and Lag columnsfor Cycle 4 occurred at < about 7.5 and about 7.5 BV, respectively.Extrapolation of the Cycle 4 Lag effluent Ca tenor data indicated thatthe product solution would have a Ca tenor > about 10 mg/L after 60BV's.

The Mg tenors of the Lag effluent for each IX cycle are plotted againstcumulative BV in FIG. 14. It is clear that the Mg tenor in the Lageffluent never approached a level close to the level of about 10 mg/L.

The average Li tenors of the Lead effluent for each IX cycle are plottedagainst cumulative BV in FIG. 15. Also included in this plot are theaverage Li tenors of the feed solutions. The data indicated thatsubstantially no Li loaded onto the resin.

The Li, Ca and Mg tenors in the Acid Strip effluents of Cycle 1 and 2are plotted against cumulative BV in FIG. 16. The data indicate that Liis stripped first from the resin and reaches for example an upper limittenor in the range of about 0.5 and about 1.5 BV's. The Ca and Mg elutedfrom the resin starting around 1 BV and both reach for example an upperlimit tenor at about 2 BV. The three metals are eluted from the resinafter 3 BV's. The Ca and Mg profiles for Cycle 3 and 4 were similar.

Reagent consumptions are reported relative to the LCE produced on a kgper about 1000 kg basis. The lithium sulphate stream produced from IonExchange contained about 39.1 kg of Li (this includes 100% of thelithium units in a PIR PLS sample that did not undergo SIR and IX). Theequivalent mass of lithium carbonate that could be produced given nolosses in downstream processes would equal about 187.7 kg.

The IX circuit produced about 2006 L of product solution. The assay dataof the IX Product solutions are summarized in Table 9. The Li tenorranged from about 15.7 to about 21.9 g/L. The ranges of the Ca and Mgtenors were about 2.4 to about 5.7 mg/L and < about 0.07 to about 0.2mg/L, respectively. Other constituents of note were Na and K at about3.5 g/L and about 0.1 g/L on average, respectively. The elements thatassayed below the detection limits of the analytical technique are alsolisted in Table 9.

TABLE 9 IX Product Solution Assays IX Solution Tenor, mg/L Product LiSO4 Cl Na K Ca Sr Mg Ba Carboy 1 15700 120000 5 3980 107 3.8 0.61   0.2 0.03  Carboy 2 16700 120000 4 1990 105 5.7 0.9    0.18 0.043 Carboy 321900 160000 5 4470 117 2.4 0.74 <0.07 0.05  Elements Assaying belowDetection (Detection Limits provided in mg/L) Ag A As Be Bi Cd Co Cr CuFe <0.5 <0.8 <3 <0.002 <1 <0.3 <0.3 <0.2 <0.1 <0.2 Mn Mo Ni P Pb Sb SeSn Ti Tl <0.04 <0.6 <1 <5 <2 <1 <3 <2 <0.1 <3 U V W Y Zn <1 <0.07 <2<0.02 <0.7

The mass balance for the IX circuit is provided in Table 10. Goodaccountability for Li was obtained. About 2.7% of the Li was lost in theStrip/Regeneration process solution. The process removed about 97.6% ofthe Ca and about 99.0% of the Mg contained in the feed solutions.

The IX circuit met the process objectives by reducing the Ca and Mgtenors in the product solution to below about 10 mg/L for each metalcation. Further, a high quality lithium sulphate solution was produced.

TABLE 10 IX Mass Balance Assays, mg/L or % Process Stream kg or L Li CaMg SIR Feed C1 750 16480 176 28.2 SIR Feed C2 682 17600 140 12.9 SIRFeed C3 359 21940 78.7 3.6 SIR Feed C4 364 21940 78.7 3.6 IX ProductCarboy 1 914 15700 3.8 0.2 IX Product Carboy 2 478 16700 5.7 0.18 IXProduct Carboy 3 614 21900 2.4 <0.07 IX Regen Reject Drum 1 202 16.935.5 2.47 IX Regen Reject Drum 2 208 12.2 16.7 <0.07 IX Strip-Solids 0.80.002 26.5 0.0004 IX Strip-Solution 111 8760 718 229 Elemental MassesIN, kg Process Stream Li Ca Mg SIR Feed C1 12.36 0.13 0.02 SIR Feed C211.99 0.10 0.01 SIR Feed C3 7.87 0.03 0.00 SIR Feed C4 7.99 0.03 0.00Total IN, kg 40.2 0.28 0.03 Elemental Masses OUT, kg Process Stream LiCa Mg IX Product Carboy 1 14.35 0.00 0.00 IX Product Carboy 2 7.99 0.000.00 IX Product Carboy 3 13.45 0.00 0 IX Regen Reject Drum 1 0.00 0.010.00 IX Regen Reject Drum 2 0.00 0.00 0 IX Strip-Solids 0.00 0.22 0.00IX Strip-Solution 0.97 0.08 0.03 Total OUT, kg 36.8 0.32 0.03Distribution, % Product 97.3 2.4 1.0 Tails 2.7 97.6 99.0 DistributionTotal 100.0 100.0 100.0 OUT/IN, % 91.4 112.4 80.3 Li Loss, % 2.7 MRemoved, % 97.6 99.0

Examination of the semi-quantitative x-ray diffraction (SQ-XRD) data ofcomposite samples of the CL/PIR residues showed that each samplecontains both α- and β-spodumene. The SQ-XRD data for the CL/PIRresidues generated from each of the two feed samples (75/25 and 50/50)are summarized in Table 11. The presence of α-spodumene indicates thatthe phase transition step that was conducted by a third party vendor(acid roast of α-spodumene) was not 100% efficient. Any Li present inthis form would thus not be chemically available to thehydrometallurgical process. It should be noted that the efficiency ofthe phase transition step (conversion from α-spodumene to β-spodumene)is not 100% and therefore a percentage of the contained Li in the feedto the Hydrometallurgical process is as α-spodumene.

TABLE 11 SQ-XRD Data of the two CL/PIR Residue Types 75/25 CL/PIR 50/50CL/PIR Chemical Residue Drum Residue Drum Composition 1-5, wt % 7-14, wt% H(AlSi₂)O₆ 60.6 67.3 Spodumene beta 12.0 9.4 SiO₂ 11.6 7.5 NaAlSi₃O₈3.6 3.8 CaSO₄•(H₂O) 2.7 4.4 KAlSi₃O₈ 1.6 3.6 LiAlSi₂O₈ 2.2 2.5Ca(SO₄)(H₂O)_(0.5) 2.5 — αFeO•OH 1.9 — Fe₃O₄ — 1.6 CaSO₄•2H₂O 1.1 —gamma-Mn₃O₄ 0.3 — 100.1 100.1 Li Bearing Mineral Relative Distributionof Li, % Spodumene beta 94.9 92.7 LiAlSi₂O₆ 5.1 7.3

The Li units that are in the CL/PIR residues as β-spodumene were neveravailable to the process and as a result provide a false low Li recoveryvalue.

An adjusted Li recovery was calculated that did not consider the Liunits tied up as β-spodumene in the CL/PIR residue. The data for thiscalculation are summarized in Table 12. The total Li in all of the outprocess streams was about 63.2 kg. This included about 11.7 kg of Li inthe CL/PIR residue that was present as β-spodumene. The adjusted totalLi out value thus becomes about 51.6 kg. The total recoverable Li by theoverall process was about 46.9 kg. The adjusted total Li recovery isthen calculated to be about 95.8%.

TABLE 12 Adjusted Total Li Recovery Li Mass, g Total Li OUT based onAssays 60615 Total Li Recovered 46884 Total Li in CL/PIR Residue asβ-Spodumene 11655 Total Li OUT minus Li as β-Spodumene 48960 AdjustedTotal Li Recovery, % 95.8

A high grade lithium sulphate solution was thus produced. In accordancewith FIG. 1, this solution can be used, for example, as the lithiumsource in the production of a solution of high quality lithium hydroxideand/or high quality lithium carbonate. This high grade lithium sulphatesolution can also be used as a feed in the production of other highgrade lithium products.

EXAMPLE 2 Electrolysis: Conversion of Li₂SO₄ into LiOH I. Introduction

Nafion™ 324 cation exchange membrane was used. This membrane is areinforced perfluorinated bi-layer membrane with sulfonic acid exchangegroups designed, for example to reduce the backmigration of hydroxidegroups (resulting in a higher current efficiency). This can be achievedby placing the higher equivalent weight polymer layer facing thecathode. It can also be used at elevated temperatures. Some alternate,for example less expensive cation exchange membranes may also besuitable for the processes of the present disclosure, such as Nafion902, Fumatech FKB and Neosepta CMB.

Two different anion exchange membranes were tested herein. The Asahi™AAV anion exchange membrane is a weakly basic, proton blocking membraneused, for example in acid concentration applications. This membrane wastested at about 40° C. The second anion exchange membrane tested hereinwas the Fumatech FAB membrane. This membrane is an acid stable protonblocking membrane with excellent mechanical stability, and can withstandhigher temperatures. It was tested at about 60° C. Higher operatingtemperatures may, for example require less cooling of the process feedsolution before it enters the electrolysis process as well as reduce theoverall energy consumption by increasing solution and membraneconductivities. It may also, for example decrease the amount of heatingrequired for the lithium hydroxide stream in the crystallization loopand for the feed returned to the dissolution step.

II. Experimental

The present experiments were carried out in an Electrocell MP cellequipped with a DSA-O₂ anode, stainless steel cathode, and one pair ofanion/cation exchange membranes. The feed loop consisted of an insulatedabout 5 liter glass reservoir with a 600 watt tape heater wrapped aroundit. The solution was circulated with an Iwaki™ VVMD-30LFX centrifugalcirculating pump. The solution pH, flow rate, temperature, and inletpressure (to the cell) were all monitored and controlled. The solutionconductivity was also monitored. Acid (or base) when needed, was addedto the feed solution for pH control using a peristaltic pump and agraduated cylinder as a reservoir.

The anolyte loop comprised an insulated about 2 liter glass reservoirwith a 300 watt heating tape wrapped around it. The solution wascirculated with a similar pump to the one described above. The solutionflow rate, temperature and inlet pressures were also monitored andcontrolled. Dilution water (for control of the concentration) was addeddirectly to the reservoir using an adjustable flow rate peristalticpump. This reservoir was allowed to overflow into a larger polypropylenecollection reservoir from which the solution was then circulated back tothe glass reservoir via peristaltic pump. The catholyte loop wassubstantially similar to the anolyte loop.

The electrode reactions are as follows:

Cathode: H₂O+e⁻→½H₂+OH⁻

Anode: H₂O→½O₂+2H⁺+2 e⁻

A diagram of the cell configuration is shown in FIG. 17.

The entire electrolysis setup was contained within a fume hood tofacilitate proper venting of the hydrogen and oxygen produced at theelectrodes.

Samples were taken during the experiments and analyzed for acidity andalkalinity using a simple acid/base titration. Selected samples werealso analyzed for anions (sulfate) and cations (lithium and sodium) byIon Chromatography.

III. Results and Discussion Experiments with Nafion 324/Asahi AAVmembranes at about 40° C.

Two experiments (856-04 and 856-11) were conducted in thisconfiguration. Table 13 summarizes the parameters used in thisexperiment. A constant about 6.8 volts was applied for both experiments.This voltage was initially chosen based on prior experience regardingthe operating conditions of these membranes.

TABLE 13 Summary of Results with AAV. *Corrected for Na added by KOHused for neutralization of sample prior to IC analysis. Experiment#856-04 856-11 Membranes NAF324/AAV NAF324/AAV Temperature (° C.) 40 40Mode Constant 6.8 V Constant 6.8 V Charge Passed (moles e/% theory Li)5.73/58.3 5.01/100.7 Time (hr) 14.25 12.78 Avg CD (mA/cm²) 107.7 105Init [H₂SO₄] (molar) 0.24 0.49 Final [H₂SO₄] (molar) 0.97 0.53 Acid CE62.4 65.1 Acid water transport (mol/mol SO₄) 1.6 −2.7 [Li] and [Na] ininitial acid (mMolar) 0/0* 0/2.4* [Li] and [Na]* in final acid (mMolar)0/0* 0/2.1* Init Base [Li]/[Na]/[OH] (molar) 0.49/0/0.46 3.1/0.18/2.85Final Base [Li]/[Na]/[OH] (molar) 2.97/0.18/3.13 3.55/0.23/3.63 Base CE82.4 73.3 Base water transport (mol/mol Li + Na 7.4 7.0 [SO₄] in baseinitial/final (mMolar) 0.4/1.9 1.9/1.8 Init Feed [Li]/[Na]/[SO₄] (molar)3.27/0.18/1.68 3.18/0.18/1.65 Final Feed [Li]/[Na]/[SO₄] (molar)2.39/0.08/1.25 1.95/0.05/0.90 % Li Removal 33.4 62.3 LiOH for pH controlat 4.0 (% of charge) 18.2 5.7 Li mass balance % 103 99 SO4 mass balance% 101.5 97

In the first experiment (#856-04), both acid and base concentrationsstarted at approx. 0.5 N (about 0.25 M sulfuric acid) and were allowedto increase through the electrolysis. The acid strength was allowed toreach about 1 M before being held constant there by the addition ofdilution water, whereas the base concentration was allowed to continueincreasing. A graph of the concentrations and the resultant currentefficiencies is shown in FIG. 18.

A final base concentration of about 3.13 M was achieved at an overallcurrent efficiency of about 82%. The overall acid current efficiency wasabout 62% with a final acid strength of about 0.97 M.

The feed pH was reduced initially during the experiment down toapproximately 4 by the addition of acid and then maintained there. Thisrequired metering in lithium hydroxide under pH control, which alsoindicates that the cation exchange membrane was performing moreefficiently than the anion exchange membrane. The amount of lithiumhydroxide required to maintain this pH accounts for about 18% of thecharge and, as expected, is close to the difference between base andacid current efficiencies. The overall current density was about 108mA/cm² for an about 33% of theory lithium removal.

The water transport, which is a measure of the amount of watertransported with the ions across the membranes was measured at about 7.4moles/mole of Li+Na across the Nafion 324 membrane into the basecompartment and about 1.6 moles/mole sulfate across the Asahi AAVmembrane into the acid compartment.

In the second experiment (#856-11) with this membrane configuration, theacid strength was kept constant at a reduced concentration of about 0.5M, and a higher base concentration (about 2.85 M) was used initially andallowed to rise up to about 3.63 M. In addition, less starting feed wasused so that higher depletion could be achieved. Under these conditions,less lithium hydroxide (corresponding to about 6% of the current) wasneeded to maintain the feed pH at about 4.0, indicating that while theefficiency of both membranes were closer together, the Nafion 324membrane efficiency remained higher than that of the AAV membrane. Agraph of the concentrations and the resultant current efficiencies isshown in FIG. 19.

The overall base current efficiency was about 73% and the acid currentefficiency was about 65%. The difference in efficiencies againcorresponds well to the amount of lithium hydroxide required to maintainfeed pH (about 6%). The overall current density for this experiment wasvery similar to the previous run at about 105 mA/cm² for about 62% oftheory lithium removal. The water transport rate across the Nafion 324was similar at about 7.0 moles/mole Li+Na. Water transport across theAsahi AAV was measured at about −2.7 moles/mole sulfate. (i.e. watertransport was from acid to feed due to the lower acid concentrationused).

Experiments with Nafion324/Fumatech FAB Membranes at about 60° C.Initial Baseline Tests

A total of six experiments (#856-22 to #856-63) were conducted in thisconfiguration. Table 14 summarizes the results of the first threeexperiments, which were used to determine various effects when processvariables were manipulated.

TABLE 14 Summary of Results with FAB. *Corrected for Na added by KOHused for neutralization of sample prior to IC analysis. Experiment#856-22 856-31 856-40 Membranes NAF324/FAB NAF324/FAB NAF324/FABTemperature ° C. 60 60 60 Mode Constant 6.8 V Constant 6.8 V Constant6.8 V Charge Passed (moles 6.08/95.9 11.11/136.9 14.11/124.7 e/% theoryLi) Time (hr) 15.95 44.38 45.53 Avg CD (mA/cm²) 102.2 67.1 83.1 Init[H₂SO₄] (molar) 0.46 0.48 0.70 Final [H₂SO₄] (molar) 0.99 0.79 0.915Acid CE 64.9 76.8 76.7 Acid water transport 3.0 0.14 1.17 (mol/mol SO₄)[Li] and [Na] in initial 0/1.6* 0/3.7* 0/0* acid (mMolar) [Li] and [Na]*in final 0/4.6* 0/10* 0/0* acid (mMolar) Init Base 3.08/0.20/3.081.97/0.11/1.90 2.43/0.12/2.61 [Li]/[Na]/[OH] (molar) Final Base3.44/0.24/3.52 2.69/0.14/2.61 2.81/0.12/2.70 [Li]/[Na]/[OH] (molar) BaseCE 70 72.7 74.5 Base water transport 7.3 8.3 7.1 (mol/mol Li + Na [SO₄]in base 1.6/1.8 0.9/1.9 1.8/1.9 initial/final (mMolar) Init Feed3.1/0.17/1.62 3.16/0.15/1.59 3.23/0.16/1.68 [Li]/[Na]/[SO₄] (molar)Final Feed 1.93/0.06/1.00 0.03/.003/0.018 0.67/0.007/0.42[Li]/[Na]/[SO₄] (molar) % Li Removal 55.8 99.7 91 Feed pH Controlled atNo pH control No pH control 4.0 3 to 1.6 to 3.3 3 to 1.8 Li mass balance% 100 102 104 SO4 mass balance % 101 104 94.3

In the first experiment (#856-22), the acid strength was initially about0.46 M and was allowed to rise to approx. 1 M before being held constantby the addition of dilution water. The initial lithium hydroxidestrength was about 3.08 M and allowed to rise to approx. 3.5 M beforebeing held constant; also by the addition of dilution water. A graph ofthe concentrations and the resultant current efficiencies is shown inFIG. 20.

The feed pH was preadjusted to about 4.0 and then held there. Thisinitially required addition of acid (the FAB membrane was more efficientthan the Nafion 324) but later required addition of lithium hydroxide(Nafion 324 became more efficient) as the acid strength increased abouttwofold and the proton backmigration into the feed compartmentincreased. The cell was run under the same constant voltage (about 6.8Vat the cell) as the experiments with the Asahi AAV membrane. The overallacid current efficiency was measured at about 65% and the base currentefficiency at about 70%.

The average current density achieved was about 102 mA/cm². A graph ofthe profiles for current density, pH and conductivity is shown in FIG.21.

A sudden increase in current density up to about 123 mA/cm² was observedduring the first portion of the experiment, followed by a gradualdecline over the rest of the experiment. While not wishing to be limitedby theory, this increase is thought to be related to the increase insulfuric acid strength during this time which helps to decrease theresistance of the FAB membrane. The conductivity of the FAB membrane canbe dependent on its pH (for example, the FAB membrane can have aresistance of about 50 Ω cm² in about neutral sodium sulfate solutionbut it can decrease to about 16 Ω cm² in about 0.5 M sulfuric acidsolution (both measurements at about 25° C.) which is a function of thetwo solutions that it divides i.e. it is a function of both the feed pHand the concentration of the acid. The peak of current density andconductivity occurring midway through the experiment was due to thesolution temperatures exceeding the setpoint of about 60° C. at thestart of the second day of the two day experiment before settling down.

The amount of lithium removal in this run was low at about 56%, whichwas due to the length of time required to treat a minimal volume offeed. The apparatus was modified so that it could be run continuouslyovernight which would allow larger volumes to be treated to completion.The next experiment was run in this manner and other modifications weremade, for example to try to increase current density and efficiency. Theacid and base concentrations were started at lower concentrations withthe goal to run for the majority of the time at lower concentration withhigher efficiency and then, by stopping water addition, allow theconcentration of both to increase to the desired values. The otherchange made was to run the feed at a lower pH (pH about 3 or below) totry to decrease the resistance of the FAB membrane.

A significantly different and lower current density profile was observedas shown in FIG. 22. The lower acid and base concentrations would have alower conductivity and would contribute to the lower current density butis not large enough to account for all of the decrease observed. Whilenot wishing to be limited by theory, observations on disassembly ofcells after later runs suggest that the main contribution may be foulingat the surface of the Nafion N324 membrane. This fouling seems to becarbonate formation at the membrane surface (on the feed side) and islikely formed during periods of time when the system is not running.Membranes removed later in the work had a small amount of whiteprecipitate which was easily removed with acid (gas was formed). It isunclear if this formed when running the feed at higher pH or when thecell was drained and carbon dioxide from air was allowed to react at thesurface of the membrane (with high pH). In either case, low currentdensity was not seen to be a problem when the system was run at lowerpH.

The current density improved considerably once the feed pH reached about2 (setting on the pH meter did not allow logging of pH below about 2).The experiment was set to turn off during the night at an estimatedamount of charge. However, since the efficiency of the process wasslightly better than estimated, the cell continued to run and the feedwas almost totally depleted (about 99.7% Li removal). Although aboutfull depletion was possible, the current density plummeted. Fulldepletion can also be detrimental to the membrane as any impurities inthe system are forced to transport through the membrane. The pH at theend of the experiment also increased dramatically, as the lithium/sodiumconcentration became comparable to the proton transport. At this pointthe concentration of sulfate was about 18 mM and was mostly present asbisulfate.

The final acid and base concentrations were lower than the previous runat about 0.8 M and about 2.6 M respectively. The lower concentrationsproduced higher overall current efficiencies at about 77% for acidproduction and about 73% for base production. The concentrations andcurrent efficiency calculated over the course of the run are shown inFIG. 23.

The current efficiency for lithium hydroxide production is dependentprimarily on its concentration and also on the pH of the feed solution.Higher concentrations of lithium hydroxide result in higherbackmigration of hydroxyl species across the cation membrane and thuslower current efficiencies. Likewise, the lower the pH of the feedsolution, the more protons are available to compete with lithium ion fortransport into the catholyte compartment, also resulting in lowercurrent efficiency. The lithium hydroxide concentration was alsoimpacted by running the feed to completion. During the period of lowcurrent, lower current efficiency would have occurred, along with alarge amount of osmotic water shift from the low concentration feed intothe base. This effect is reflected in the relatively high rate of watertransport measured of about 8.3 mol water per mol of lithium/sodiumtransported.

In addition, the pH of the feed compartment is also very dependent onthe concentration of acid being produced. The higher the concentrationof acid product, the more protons migrate across the anion membrane intothe feed compartment, resulting in lower acid current efficiency as wellas lower feed pH (which impacts the caustic current efficiency asdiscussed above).

The cell was rebuilt with new membranes and a repeat of the previousexperiment was performed except that higher start acid and baseconcentrations were used. FIG. 24 shows that the acid concentration waskept from about 0.9 to about 1.0 M throughout the experiment. The basestarted at about 2.4 M and was allowed to increase to almost about 3 Mthroughout the run. Current efficiencies for acid and base productionwere about 77% and about 75% respectively.

FIG. 25 shows that the current density for this run was still relativelylow compared to the first run (856-22). It was more similar to thesecond run (856-34), but since this run was stopped earlier than 856-34,(at about 91% lithium removal instead of about 99.7%), the averagecurrent density was considerably higher at about 83 mA/cm².

The end pH of the solution was about 1.8 due to the amount of protonback migration. At this pH, about 60% of the sulfate is in solution asbisulfate with only about 0.015 M protons in solution.

N324/FAB Runs with Lower Feed pH (Production Runs)

The final set of three experiments was used to generate product for usein crystallization studies. The summary of the tests is shown in Table15. Larger volumes were used and an attempt was made to increase thecurrent density of previous runs by running the system at constant acidconcentration and lower feed pH. By running at lower feed pH, there wasnot any problem with membrane fouling between runs as was seen whenrunning the feed at the higher pH (> about 3). However, both the acidand base current efficiencies suffered. The other difference in theseruns was that additional voltage was applied to the cell: about 7.8 Vinstead of about 6.8 V. This change was made early during 856-49,resulting in an increase in current density from about 55 mA/cm² toabout 95 mA/cm². The higher voltage numbers will be used in determiningpower consumption details.

TABLE 15 Summary of Production Runs with FAB. *Corrected for Na added byKOH used for neutralization of sample prior to IC analysis. Experiment#856-49 856-56 856-63 Membranes NAF324/FAB NAF324/FAB NAF324/FABTemperature ° C. 60 60 60 Mode Constant 7.8 V Constant 7.8 V Constant7.8 V Charge Passed (moles 24.8/125.9 24.8/124.6 14.0/146.4 e/% theoryLi) Time (hr) 55.2 51.56 28.5 Avg CD (mA/cm²) 120.5 129 131.7 Init[H₂SO₄] (molar) 0.879 0.848 0.855 Final [H₂SO₄] (molar) 0.910 0.8950.888 Acid CE 58.9 58.9 58.4 Acid water transport 0.65 −0.59 0.2(mol/mol SO₄) [Li] and [Na] in initial 0/1* 0/0* 0/0* acid (mMolar) [Li]and [Na]* in final 0/2* 0/0* 0/0* acid (mMolar) Init Base 2.57/0.14/2.572.55/0.13/2.45 3.04/0.14/3.08 [Li]/[Na]/[OH] (molar) Final Base2.93/0.16/2.84 2.82/0.15/2.68 3.09/0.15/3.14 [Li]/[Na]/[OH] (molar) BaseCE 68.6 65.5 63.7 Base water transport 7.7 8.0 8.2 (mol/mol Li + Na[SO₄] in base 1.9/2.0 1.5/2.0 1.5/2.3 initial/final (mMolar) Init Feed3.24/0.17/1.71 3.27/0.17/1.78 3.11/0.13/1.87 [Li]/[Na]/[SO₄] (molar)Final Feed 1.03/0.03/1.07 1.20/0.04/1.32 1.01/0.02/1.18 [Li]/[Na]/[SO₄](molar) % Li Removal 85.4 81.6 84.4 Feed pH No pH control Acid addedAcid added 3 down to 0.8 initially to initially to maintain 1.5,maintain 1.5, then pH went then pH went down to 0.73 down to 0.79 Limass balance % 104 104 105 SO4 mass balance % 103 102 104

Graphs showing concentrations and current efficiencies are shown inFIGS. 26 to 31. Starting the system at a lower pH and allowing the feedpH to decrease was detrimental to the current efficiency of the process.The feed pH can be better controlled in a commercial plant situationthan in these laboratory experiments. In the longer term runs, sulfuricacid was added to the feed to bring its pH from about 10 down to about 3before the start of the experiment. This was done for the completevolume of feed, and then the feed pH continued to decrease in operation.However, in a plant, a smaller heal of feed solution could be acidifiedand more feed at pH about 10 can be added as the experiment continues.Similar benefits occur if the process is run continuously instead of inbatch mode. It is estimated from these experiments that over half of theacid in the feed at the end of the experiment was due to acidpretreatment. By adding the feed continuously, the proton concentrationcan be decreased from about 0.15 M to about 0.075M which would increasethe measured current efficiencies.

Although small changes were made in the last three runs to increase theachievable current density, the results obtained were very consistentand reproducible. Slight changes in the base current efficiency andwater transport are due to changes in feed pH. During the testing about25 L of lithium hydroxide and about 45 L of sulfuric acid was produced.

III. Conclusions

It has been shown that lithium hydroxide can be successfully recoveredat high efficiencies from a lithium sulfate process stream attemperatures of about 40° C. or about 60° C., using electrolysis withNafion 324 cation exchange membrane and either Asahi AAV or Fumatech FABanion exchange membranes. Both anion membranes were efficient at acidproduction, but the FAB membrane allowed higher acid concentrations atsimilar current efficiencies. The FAB membrane can also be run at highertemperatures (about 60° C.) which therefore, for example may decreasethe amount of required cooling. Based on these considerations, thefollowing process was defined using a combination of N324 and FAB.

Process using N324/FAB membranes

Based on the testing performed, the process would be expected to havethe following characteristics:

-   -   Sulfuric acid produced at a concentration of about 0.75 M    -   Lithium Hydroxide produced at a concentration of about 3.2 M    -   Average Current Density of about 100 mA/cm²    -   Current efficiency of about 75%    -   Cell Voltage of about 6 V (see below for calculations)    -   Water transport from feed to base of about 8 mol water per mol        cation    -   Water transport from feed to acid of < about 1 mol water per mol        cation.

The cell voltage for the process in the MP cell was about 7.8 V.However, the lab cell has very large flow gaps between electrode andmembranes (about 10 mm) which would be substantially reduced in thelarger plant cell. The gap can typically be reduced to about 2 mm whichwill remove about 1.8 V from the total cell voltage (based on acid, baseand feed conductivities of about 275 mS/cm, about 400 mS/cm and about 70mS/cm, respectively.). Using this reduced cell voltage and predictedcurrent efficiency, the process would require a power consumption ofabout 8.9 kWh/kg of LiOH. (in an about 3.2 M solution). For a plantproducing about 3 tonne/hour of LiOH, the plant would contain about 4500m² of cell area, which would be a large electrochemical plant comparableto a moderate sized chlor-alkali plant. Other than when running athigher pH, there were no stability issues found for the membranes orelectrodes.

Summary

It has been shown in the studies of the present disclosure that lithiumhydroxide can be successfully recovered at high efficiencies from alithium sulfate process stream at temperatures of about 40° C. or about60° C., using electrolysis with a Nafion 324 cation exchange membraneand either an Asahi AAV or a Fumatech FAB anion exchange membrane. Inboth cases, sulfuric acid was produced as the coproduct.

The Nafion 324 membrane was used in both electrolysis configurationstested. The cation membrane had very good efficiency for lithiumproduction, making up to about 3.6 M hydroxide at a current efficiencyof over about 70%. A higher efficiency at a lower concentration wasshown to be possible, but the inefficiency of the anion membranes limitsthis need. While not wishing to be limited by theory, a lower acidefficiency effectively decreases the pH of the feed solution, resultingin either the use of some of the produced lithium hydroxide to maintainthe pH or the competition of proton with lithium/sodium across thecation membrane. This effectively makes the efficiency of the processequal to the lowest efficiency of the two membranes.

The lithium sulfate feed contains a large concentration of sodium ion.The cation membrane is not selective and therefore the produced basecontains sodium ion in roughly the same ratio as that found in the feed.The base also contained about 2 mM (about 200 ppm) of sulfate.

It was possible to obtain similar current densities of about 100 mA/cm²incorporating both Asahi AAV (at about 40° C.) and Fumatech FAB membrane(at about 60° C.). However, the AAV membrane gave current efficienciesof less than about 65% when the acid concentration was above about 0.5M. The FAB acid efficiency was more dependent on acid concentration,giving about 75% current efficiency at about 0.9 M acid concentration.The acid efficiency dropped considerably above this value.

The current densities achieved when using the FAB membrane were verydependent on the pH of the feed solution (due to its higher resistanceat higher pH). It was necessary to maintain a lower feed pH in order toachieve similar current densities to those with AAV membrane. This wasdone either by increasing the strength of the acid produced and thusalso the backmigration of protons across the anion membrane into thefeed compartment, or by running at a lower feed pH. Both conditions werefound to result in a lower current efficiency for acid production aswell as for production of lithium hydroxide by increasing the proton/Liratio in the feed and thus also proton competition into the catholytecompartment.

Based on the testing performed in the studies of the present disclosure,the process would be expected to have the following characteristics:

-   -   Sulfuric acid produced at a concentration of about 0.75 M    -   Lithium hydroxide produced at a concentration of about 3.2 M    -   Average current density of about 100 mA/cm²    -   Current efficiency of about 75%    -   Cell voltage of about 6 V (in an engineered cell for the        process)    -   Water transport from feed to base of about 8 mol water per mol        cation    -   Water transport from feed to acid of < about 1 mol water per mol        cation.

Although the above-described process shows promise, an alternate processwhere ammonium sulfate is produced instead of sulfuric acid may also beemployed and details of that process along with at least some of itsbenefits are given below in Example 3.

EXAMPLE 3 Alternate Process using Ammonia to Neutralize Acid

The current work has been successful at producing higher strength baseand acid with higher current efficiency than both bipolar membraneelectrodialysis (ED) and other development work previously carried out.However, the anion membrane that was used for this process is aproton-blocking membrane which has a high resistance especially forsulfate transport and has limited the current density achieved. Thesemembranes can be limited to about 60° C.

To resolve at least some of the above-mentioned difficulties, a highconcentration of ammonium sulfate (> about 2 M) can be produced in asimilar electrolysis cell, and due to the buffering capacity ofbisulfate and the ability to dissolve ammonia in solution, it ispossible to make the anolyte solution non-acidic as shown in FIG. 32. Inthis way, proton blocking membranes, for example may not be required andalternative membranes, for example Neosepta AHA, which are capable ofrunning at about 80° C. and that should have lower resistance can beused.

This will, for example allow operation at higher temperature requiringless cooling of solutions. Solutions and membranes are also lessresistive at these higher temperatures, decreasing power consumption. Itmay also, for example remove the higher resistance FAB membrane,possibly allowing operation at either higher current density (therebyreducing membrane area), lower voltage (thereby reducing powerconsumption) or a combination of the two. It may also, for examplegenerate an alternate commercial material. Ammonium sulfate can be soldas an ingredient for fertilizer and should have a higher value than thesulfuric acid. It is also, for example expected to remove more waterduring the electrolysis from the feed thereby allowing more efficientoperation over a wider range of feed conversion.

EXAMPLE 4 Production of Lithium Hydroxide from Lithium Sulfate usingThree-Compartment Bipolar Membrane Eletrodialysis

A base solution at a concentration of 2 N containing 78% of Li⁺ can beproduced from a Li₂SO₄ salt containing 83% of Li⁺, using athree-compartment Bipolar Membrane Electrodialysis (EDBM) stack.Practically, the corresponding maximum concentration of the sulfuricacid produced is 1.5 N.

I. Introduction

The present studies investigated the splitting of lithium sulfate toproduce lithium hydroxide and sulfuric acid using a three-compartmentBipolar Membrane Electrodialysis stack.

The technology used to achieve the conversion of lithium sulfate intoits acid and base, is the three compartment EDBM stack shown in FIG. 33.The system has 3 compartments: one for the salt stream (Li₂SO₄); one forthe base recovery (LiOH); and one for the acid recovery (H₂SO₄)

When an electric field is applied to the system, the cations (here Li⁺,Na⁺, K⁺ and Ca²⁺) can migrate from the salt, through the cation membrane(C), into the base loop. The anions (SO₄ ²⁻) can migrate through theanionic membrane (A) into the acid loop. The bipolar membrane (BP) canact as a H⁺ and OH⁻ generator by splitting the water molecules duringthe process. The reaction of the H⁺ and OH⁻ with the ions moving fromthe salt into their respective compartments allows the formation of theacidic and basic solutions.

II. Materials and Methods

The lithium sulfate used in the present studies had the followingcharacteristics detailed in Table 16:

TABLE 16 Chemical characteristics at room temperature of Li₂SO₄ pH 10.83Conductivity (mS/cm) 86.2 Li⁺ (g/L) 23.4 Na⁺ (g/L) 4.46 K⁺ (g/L) 0.13Ca²⁺ (g/L) 0.003

Lithium represented 83% of the feed total cations content. All of theother ions present in the solution migrated according to their initialproportions in the salt stream.

The EUR2 stack used for the experiments was composed of seventhree-compartment cells. The salt solution was at room temperature and aflow rate of 190 L/h (0.8 GPM) was used for the trials. The feed wasacidified to pH 1-2 with sulfuric acid, which is a useful pH for theanionic membrane.

Eight trials were conducted according to the parameters shown in Table17 below. The 4th trial has been divided in 3 smaller trials (systemstopped, volume measured and samples taken) to evaluate the effect ofthe acid and base concentrations on the current efficiency. For thepurpose of this work, the results obtained for Trials 4, 5, 6 and 8 werecompared. Trials 5, 6 and 8 are triplicates that have been done with thesame initial conditions to investigate the repeatability of the results.

TABLE 17 Trials parameters Acid Base Salt Trial Volume ConcentrationVolume Concentration Volume No. (L) (N) (L) (N) (L) 1 4 0.263 4 0.148 42 3 0.91 3 0.93 5 3 3 0.56 3 0.65 3.4 4.1 2 0.225 2 0.23 5 4.2 2 1.073 21.16 4.5 4.3 1.9 2.055 2.2 2.03 4 5 2 0.1 2 0.875 3.9 6 2.5 0.76 2.11.08 3.9 7 2.5 0.705 2 1.08 4.1 8 2 0.67 2 0.805 4.1

During the eight trials, no significant increase of the voltage or theresistance of the system was observed. While not wishing to be limitedby theory, this indicates that the product is usefully clean and doesnot appear to have significantly affected the membranes under theconditions and for the amount of time used to complete the trials forthis study.

FIG. 34 shows the evolution of current over time for Trials 4, 5, 6 and8. FIG. 35 shows the increase of the base conductivity as a function oftime. The increase rate is similar for all the trials. FIG. 36 shows theincrease of the acid conductivity as a function of time.

During Trials 6 and 8, water was added to the acid tank to maintain aconcentration below about 1.5N. At higher concentrations, the acidconcentration negatively influences the overall current efficiencybecause the acid current efficiency becomes much lower than the baseefficiency. While not wishing to be limited by theory, this is due tothe anionic membrane allowing the H⁺ ions to transport when theirconcentration becomes too high (see FIG. 37).

The impact of producing a highly concentrated base or acid has beenstudied during Trial 4. This trial was separated into three sub-trialsfor which initial and final samples have been collected. The samesolutions of acid, base and salt were used to increase theirconcentration as much as possible. FIG. 38 shows the decrease of thecurrent efficiency observed for Trial 4 function of the concentration ofthe acid and the base.

Table 18 shows the different parameters obtained for each trial, as wellas the current efficiency. The current efficiency decreased by more than20% during Trials 4; from about 60% to 36% as the concentrationincreased from 1.1N to 2.6N for the acid and from 1.2 to 2.4N for thebase. Trials 5, 6 and 8 are similar: these trials show that, by keepingthe acid concentration under about 1.5N and the base concentration at amaximum of about 2N by adding water during the batch, the averagedcurrent efficiency is 58%. The overall current efficiency of the processis determined by the lowest current efficiency between the acid and thebase.

TABLE 18 Trials parameters and titration results. Trial No. 4 4-1 4-24-3 5 6 8 Time (min) 155 65 55 35 105 85 75 Temperature (° C.) 36.830.93 39.34 40.52 39.03 37.22 36.37 Intensity (A) 14.39 10.00 14.0020.00 16.48 14.24 14.40 Current density (mA/cm²) 71.95 50.00 70.00100.00 82.38 71.18 72.00 Volt/cell 2.44 2.8 2.7 2.8 mol water/mol Li⁺transferred 2.31 5.37 5.42 3.98 Acid initial concentration (N) 0.2250.225 1.075 2.059 0.100 0.760 0.670 Acid final concentration (N) 2.6101.075 2.059 2.610 1.890 1.390 1.430 Base initial concentration (N) 0.2300.230 1.160 2.030 0.875 1.085 0.805 Base final concentration (N) 2.4001.160 2.030 2.400 2.180 2.230 2.000 Q th 9.71 2.83 3.36 3.05 7.53 5.274.70 Qa (%) 49.14 60.09 58.72 36.17 59.43 56.30 56.67 Qb (%) 49.65 65.7551.92 40.04 54.91 58.36 59.36

Table 19 shows the salt conversion ratio and current efficiency for thebase according to the cations analysis results obtained. The highestconversion rate obtained was 31% but could have been higher bycontinuing to convert the same solution for more than one trial (whenthe acid and base reached the maximum concentrations). For the purposeof this study, the salt was changed for each trial to keep the sameinitial conditions. Therefore, while not wishing to be limited bytheory, the relatively low conversion rate is due to the choice of thetesting conditions.

TABLE 19 Salt conversion and current efficiency based on the total Li⁺,Na⁺, K⁺ and Ca²⁺ content of each fraction. Trial No. 4 4-1 4-2 4-3 5 6 8Salt In (eq/L) 3.34 3.34 3.10 2.59 2.80 3.50 3.55 Salt Out (eq/L) 2.413.10 2.59 2.41 1.92 2.64 2.85 Conversion (%) 28.05 7.37 16.28 7.22 31.1524.73 19.72 Base In (eq/L) 0.34 0.34 1.12 1.93 0.89 1.12 0.82 Base Out(eq/L) 2.41 1.12 1.93 2.41 2.17 2.26 1.99 Current efficiency Base (%)47.49 55.32 48.17 46.94 54.21 58.20 58.15

The current efficiencies obtained by the base analysis confirm thoseobtained by titration for Trials 5, 6 and 8 and the decrease ofefficiency observed as a function of the increasing concentration forTrial 4. The chemical analysis of the base showed that the final basecontained 78% of lithium (see Table 20 for all chemical results).

TABLE 20 Chemical analysis results. Li Na K Ca Total Sample ID (mg/L)(mg/L) (mg/L) (mg/L) (eq/L) In-Product T1-T5 23400 4460 127 3.2 3.51In-Product T6-T8 23200 4360 129 3.2 3.47 4.1 Salt-In 22300 4360 121 3.23.34 4.2 Salt-65 min 21500 — — — 3.10 4.3 Salt-120 min 18000 — — — 2.594.4 Salt-F 16300 1940 28 2.7 2.41 5.1 Salt-In 18600 3830 115 2.9 2.805.2 Salt-F 13000 1740 23 2.1 1.92 6.1 Salt-In 23300 4820 128 3.2 3.506.2 Salt-F 17700 2870 54 3.3 2.64 8.1 Salt-In 23600 4900 139 3.3 3.558.2 Salt-F 19100 3220 66 3 2.85 4.5 Acid-In 461 — — — 0.07 4.6 Acid-65min 577 — — — 0.08 4.7 Acid-120 min 639 — — — 0.09 4.8 Acid-F 646 — — —0.09 5.3 Acid-In 102 — — — 0.01 5.4 Acid-F 236 — — — 0.03 6.3 Acid-In 75— — — 0.01 6.4 Acid-F 125 — — — 0.02 8.3 Acid-In 79.8 — — — 0.01 8.4Acid-F 129 — — — 0.02 4.9 Base-In 2270 469 11 1.5 0.34 4.10 Base-65 min7800 — — — 1.12 4.11 Base-120 min 13400 — — — 1.93 4.12 Base-F 159003800 126 3.9 2.41 5.5 Base-In 5890 1360 43 1.6 0.89 5.6 Base-F 143003770 124 3.3 2.17 6.5 Base-In 7340 2040 45 2.3 1.12 6.6 Base-F 148004110 134 3.7 2.26 8.5 Base-In 5320 1760 45 1.4 0.82 8.6 Base-F 131003270 133 2.6 1.99

III. Conclusions

This example shows that the conversion of lithium sulfate into lithiumhydroxide and sulfuric acid is useful up to concentrations of about 2Nfor the base and about 1.5N for the acid. The conversion of the salt maybe increased by continuing to convert the same salt solution when theacid and base reach these concentrations. Based on the obtained results,the Bipolar Membrane Electrodialysis technology appears to be useful.

While a description was made with particular reference to the specificembodiments, it will be understood that numerous modifications theretowill appear to those skilled in the art. Accordingly, the abovedescription and accompanying drawings should be taken as specificexamples and not in a limiting sense.

What is claimed is:
 1. A system for preparing lithium hydroxide, saidsystem comprising: an electrolysis cell, said electrolysis cell definingan anodic compartment separated from a central compartment by an anionexchange membrane and a cathodic compartment separated from said centralcompartment by a cation exchange membrane, said central compartmentcomprising at least one inlet for receiving an aqueous compositioncomprising lithium compound, said cathodic compartment comprising atleast one cathode wherein said cathode is configured to produce alithium hydroxide-enriched aqueous composition, said anodic compartmentcomprising at least one anode, wherein said system further comprises apH probe and at least one inlet for receiving acid or base for at leastsubstantially maintaining the pH of said aqueous composition comprisingsaid lithium compound at about 1 to about
 4. 2. The system of claim 1,wherein said electrolysis cell is a monopolar electrolysis cell.
 3. Thesystem of claim 2, wherein said pH probe and said at least one inlet forreceiving acid or base are for at least substantially maintaining the pHthe pH of said aqueous composition comprising said lithium compound ismaintained at about 2 to about
 4. 4. The system of claim 3, wherein saidpH probe and said at least one inlet for receiving acid or base are forat least substantially maintaining the pH of said aqueous compositioncomprising said lithium compound is maintained at about
 2. 5. The systemof claim 1, wherein said cathodic compartment further comprises at leastone inlet for receiving an aqueous composition comprising lithiumhydroxide.
 6. The system of claim 1, wherein said anodic compartmentfurther comprises at least one inlet for receiving an aqueouscomposition comprising an acid.
 7. The system of claim 6, wherein saidcathodic compartment is configured for at least substantially maintainedsaid aqueous composition comprising lithium hydroxide at a concentrationof lithium hydroxide of about 35 to about 70 g/L.
 8. The system of claim6, wherein said cathodic compartment is configured for at leastsubstantially maintained said aqueous composition comprising lithiumhydroxide at a concentration of lithium hydroxide of about 45 to about65 g/L.
 9. The system of claim 6, wherein said anodic compartment isconfigured for at least substantially maintaining said aqueouscomposition comprising said acid at a concentration of said acid ofabout 20 to about 50 g/L.
 10. The system of claim 6, wherein said anodiccompartment is configured for at least substantially maintaining saidaqueous composition comprising said acid a concentration of said acid ofabout 25 to about 35 g/L.
 11. The system of claim 1, wherein said atleast one inlet of said central compartment is for receiving saidaqueous composition comprising lithium sulphate, lithium chloride,lithium fluoride, lithium carbonate, lithium bicarbonate, lithiumacetate, lithium stearate or lithium citrate.
 12. The system of claim11, wherein said at least one inlet of said central compartment is forreceiving said aqueous composition comprising lithium sulphate.
 13. Thesystem of claim 1, wherein said at least one inlet of said anodiccompartment is for receiving sulfuric acid.
 14. The system of claim 1,wherein said central compartment is configured for maintaining saidaqueous composition comprising said lithium compound at a concentrationof said lithium compound of about 10 g/L to about 20 g/L.
 15. The systemof claim 1, wherein said system further comprises a thermometer, and atemperature control device for at least substantially maintaining saidaqueous composition comprising lithium sulfate at a temperature of about20° C. to about 80° C.
 16. The system of claim 1, wherein said systemfurther comprises a power supply comprising an ammeter for at leastsubstantially maintaining an electrical current of said electrochemicalcell of about 400 to about 3000 A/m².
 17. The system of claim 1, whereinsaid system further comprises a power supply comprising an ammeter forat least substantially maintaining an electrical current density of saidelectrochemical cell of about 400 A/m² to about 1000 A/m².
 18. Thesystem of claim 1, wherein said power supply further comprises avoltmeter for at least substantially maintaining a voltage of saidelectrochemical cell at a constant value.
 19. The system of claim 1,wherein said anodic compartment further comprises at least one outletfor outputting an oxygen-comprising stream.
 20. The system of claim 1,wherein said cathodic compartment further comprises at least one outletfor outputting said lithium hydroxide-enriched aqueous composition.